description: Theofanis started playing the new online game called "Among them". However, he always plays with Cypriot players, and they all have the same name: "Andreas" (the most common name in Cyprus).
  
  In each game, Theofanis plays with n other players. Since they all have the same name, they are numbered from 1 to n.
  
  The players write m comments in the chat. A comment has the structure of "i j c" where i and j are two distinct integers and c is a string (1 ≤ i, j ≤ n; i ≠ j; c is either imposter or crewmate). The comment means that player i said that player j has the role c.
  
  An imposter always lies, and a crewmate always tells the truth. 
  
  Help Theofanis find the maximum possible number of imposters among all the other Cypriot players, or determine that the comments contradict each other (see the notes for further explanation).
  
  Note that each player has exactly one role: either imposter or crewmate.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^4) — the number of test cases. Description of each test case follows.
  
  The first line of each test case contains two integers n and m (1 ≤ n ≤ 2 ⋅ 10^5; 0 ≤ m ≤ 5 ⋅ 10^5) — the number of players except Theofanis and the number of comments.
  
  Each of the next m lines contains a comment made by the players of the structure "i j c" where i and j are two distinct integers and c is a string (1 ≤ i, j ≤ n; i ≠ j; c is either imposter or crewmate).
  
  There can be multiple comments for the same pair of (i, j).
  
  It is guaranteed that the sum of all n does not exceed 2 ⋅ 10^5 and the sum of all m does not exceed 5 ⋅ 10^5.
  
  Output
  
  For each test case, print one integer — the maximum possible number of imposters. If the comments contradict each other, print -1.
  
  Example
  
  Input
  
  
  5
  3 2
  1 2 imposter
  2 3 crewmate
  5 4
  1 3 crewmate
  2 5 crewmate
  2 4 imposter
  3 4 imposter
  2 2
  1 2 imposter
  2 1 crewmate
  3 5
  1 2 imposter
  1 2 imposter
  3 2 crewmate
  3 2 crewmate
  1 3 imposter
  5 0
  
  
  Output
  
  
  2
  4
  -1
  2
  5
  
  Note
  
  In the first test case, imposters can be Andreas 2 and 3.
  
  In the second test case, imposters can be Andreas 1, 2, 3 and 5.
  
  In the third test case, comments contradict each other. This is because player 1 says that player 2 is an imposter, and player 2 says that player 1 is a crewmate. If player 1 is a crewmate, then he must be telling the truth, so player 2 must be an imposter. But if player 2 is an imposter then he must be lying, so player 1 can't be a crewmate. Contradiction.
solution: import java.io.*;import java.util.*;import java.math.*;import static java.lang.Math.*;import static java.
          util.Map.*;import static java.util.Arrays.*;import static java.util.Collections.*;
  import static java.lang.System.*;
  public class Main
  {
      public void tq()throws Exception
      {
          st=new StringTokenizer(bq.readLine());
          int tq=i();
          sb=new StringBuilder(20);
          o:
          while(tq-->0)
          {
              int n=i();
              int m=i();
              LinkedList<int[]> a[]=new LinkedList[n];
              for(int x=0;x<n;x++)a[x]=new LinkedList<>();
              for(int x=0;x<m;x++)
              {
                  int aa=i()-1;
                  int bb=i()-1;
                  int c=s().equalsIgnoreCase("imposter")?1:2;
                  a[aa].add(new int[]{bb,c});
                  a[bb].add(new int[]{aa,c});
              }
              int k[]=new int[n];
              int c=0;
              for(int x=0;x<n;x++)
              {
                  if(k[x]!=0)continue;
                  LinkedList<int[]> l=new LinkedList<>();
                  l.add(new int[]{x,1});
                  k[x]=1;
                  int ss=0;
                  int cc=0;
                  while(l.size()>0)
                  {
                      int s=l.size();
                      ss+=s;
                      while(s-->0)
                      {
                          int r[]=l.remove();
                          if(r[1]==-1)cc++;
                          for(int e[]:a[r[0]])
                          {
                              int t=e[0];
                              int d=e[1];
                              if(r[1]==1)
                              {
                                  if(d==2)
                                  {
                                      if(k[t]==-1)
                                      {
                                          sl(-1);
                                          continue o;
                                      }
                                      if(k[t]==0)l.add(new int[]{t,1});
                                      k[t]=1;
                                  }
                                  else
                                  {
                                      if(k[t]==1)
                                      {
                                          sl(-1);
                                          continue o;
                                      }
                                      if(k[t]==0)l.add(new int[]{t,-1});
                                      k[t]=-1;
                                  }
                              }
                              else
                              {
                                  if(d==1)
                                  {
                                      if(k[t]==-1)
                                      {
                                          sl(-1);
                                          continue o;
                                      }
                                      if(k[t]==0)l.add(new int[]{t,1});
                                      k[t]=1;
                                  }
                                  else
                                  {
                                      if(k[t]==1)
                                      {
                                          sl(-1);
                                          continue o;
                                      }
                                      if(k[t]==0)l.add(new int[]{t,-1});
                                      k[t]=-1;
                                  }
                              }
                          }
                      }
                  }
                  c+=max(cc,ss-cc);
              }
              sl(c);
          }
          p(sb);
      }
      void f(){out.flush();}
      int di[][]={{-1,0},{1,0},{0,-1},{0,1}};
      int de[][]={{-1,0},{1,0},{0,-1},{0,1},{-1,-1},{1,1},{-1,1},{1,-1}};
      long mod=1000000007l;int max=Integer.MAX_VALUE,min=Integer.MIN_VALUE;long maxl=Long.MAX_VALUE, minl=Long.
          MIN_VALUE;BufferedReader bq=new BufferedReader(new InputStreamReader(in));StringTokenizer st;
      StringBuilder sb;public static void main(String[] a)throws Exception{new Main().tq();}int[] so(int ar[])
  {Integer r[]=new Integer[ar.length];for(int x=0;x<ar.length;x++)r[x]=ar[x];sort(r);for(int x=0;x<ar.length;
                                                                                         x++)ar[x]=r[x];return ar;}long[] so(long ar[]){Long r[]=new Long[ar.length];for(int x=0;x<ar.length;x++)
      r[x]=ar[x];sort(r);for(int x=0;x<ar.length;x++)ar[x]=r[x];return ar;}
      char[] so(char ar[]) {Character
              r[]=new Character[ar.length];for(int x=0;x<ar.length;x++)r[x]=ar[x];sort(r);for(int x=0;x<ar.length;x++)
          ar[x]=r[x];return ar;}void s(String s){sb.append(s);}void s(int s){sb.append(s);}void s(long s){sb.
          append(s);}void s(char s){sb.append(s);}void s(double s){sb.append(s);}void ss(){sb.append(' ');}void sl
          (String s){sb.append(s);sb.append("\n");}void sl(int s){sb.append(s);sb.append("\n");}void sl(long s){sb
          .append(s);sb.append("\n");}void sl(char s) {sb.append(s);sb.append("\n");}void sl(double s){sb.append(s)
  ;sb.append("\n");}void sl(){sb.append("\n");}int l(int v){return 31-Integer.numberOfLeadingZeros(v);}
      long l(long v){return 63-Long.numberOfLeadingZeros(v);}int sq(int a){return (int)sqrt(a);}long sq(long a)
  {return (long)sqrt(a);}long gcd(long a,long b){while(b>0l){long c=a%b;a=b;b=c;}return a;}int gcd(int a,int b)
  {while(b>0){int c=a%b;a=b;b=c;}return a;}boolean pa(String s,int i,int j){while(i<j)if(s.charAt(i++)!=
          s.charAt(j--))return false;return true;}boolean[] si(int n) {boolean bo[]=new boolean[n+1];bo[0]=true;bo[1]
          =true;for(int x=4;x<=n;x+=2)bo[x]=true;for(int x=3;x*x<=n;x+=2){if(!bo[x]){int vv=(x<<1);for(int y=x*x;y<=n;
                                                                                                       y+=vv)bo[y]=true;}}return bo;}long mul(long a,long b,long m) {long r=1l;a%=m;while(b>0){if((b&1)==1)
      r=(r*a)%m;b>>=1;a=(a*a)%m;}return r;}int i()throws IOException{if(!st.hasMoreTokens())st=new
          StringTokenizer(bq.readLine());return Integer.parseInt(st.nextToken());}long l()throws IOException
  {if(!st.hasMoreTokens())st=new StringTokenizer(bq.readLine());return Long.parseLong(st.nextToken());}String
  s()throws IOException {if (!st.hasMoreTokens())st=new StringTokenizer(bq.readLine());return st.nextToken();}
      double d()throws IOException{if(!st.hasMoreTokens())st=new StringTokenizer(bq.readLine());return Double.
              parseDouble(st.nextToken());}void p(Object p){out.print(p);}void p(String p){out.print(p);}void p(int p)
  {out.print(p);}void p(double p){out.print(p);}void p(long p){out.print(p);}void p(char p){out.print(p);}void
  p(boolean p){out.print(p);}void pl(Object p){out.println(p);}void pl(String p){out.println(p);}void pl(int p)
  {out.println(p);}void pl(char p){out.println(p);}void pl(double p){out.println(p);}void pl(long p){out.
          println(p);}void pl(boolean p)
  {out.println(p);}void pl(){out.println();}void s(int a[]){for(int e:a)
  {sb.append(e);sb.append(' ');}sb.append("\n");}
      void s(long a[])
      {for(long e:a){sb.append(e);sb.append(' ')
      ;}sb.append("\n");}void s(int ar[][]){for(int a[]:ar){for(int e:a){sb.append(e);sb.append(' ');}sb.append
          ("\n");}}
      void s(char a[])
      {for(char e:a){sb.append(e);sb.append(' ');}sb.append("\n");}void s(char ar[][])
  {for(char a[]:ar){for(char e:a){sb.append(e);sb.append(' ');}sb.append("\n");}}int[] ari(int n)throws
          IOException {int ar[]=new int[n];if(!st.hasMoreTokens())st=new StringTokenizer(bq.readLine());for(int x=0;
                                                                                                            x<n;x++)ar[x]=Integer.parseInt(st.nextToken());return ar;}int[][] ari(int n,int m)throws
          IOException {int ar[][]=new int[n][m];for(int x=0;x<n;x++){if (!st.hasMoreTokens())st=new StringTokenizer
          (bq.readLine());for(int y=0;y<m;y++)ar[x][y]=Integer.parseInt(st.nextToken());}return ar;}long[] arl
          (int n)throws IOException {long ar[]=new long[n];if(!st.hasMoreTokens()) st=new StringTokenizer(bq.readLine())
          ;for(int x=0;x<n;x++)ar[x]=Long.parseLong(st.nextToken());return ar;}long[][] arl(int n,int m)throws
          IOException {long ar[][]=new long[n][m];for(int x=0;x<n;x++) {if(!st.hasMoreTokens()) st=new
          StringTokenizer(bq.readLine());for(int y=0;y<m;y++)ar[x][y]=Long.parseLong(st.nextToken());}return ar;}
      String[] ars(int n)throws IOException {String ar[] =new String[n];if(!st.hasMoreTokens())st=new
              StringTokenizer(bq.readLine());for(int x=0;x<n;x++)ar[x]=st.nextToken();return ar;}double[] ard
          (int n)throws IOException {double ar[] =new double[n];if(!st.hasMoreTokens())st=new StringTokenizer
          (bq.readLine());for(int x=0;x<n;x++)ar[x]=Double.parseDouble(st.nextToken());return ar;}double[][] ard
          (int n,int m)throws IOException{double ar[][]=new double[n][m];for(int x=0;x<n;x++) {if(!st.hasMoreTokens())
      st=new StringTokenizer(bq.readLine());for(int y=0;y<m;y++) ar[x][y]=Double.parseDouble(st.nextToken());}
      return ar;}char[] arc(int n)throws IOException{char ar[]=new char[n];if(!st.hasMoreTokens())st=new
          StringTokenizer(bq.readLine());for(int x=0;x<n;x++)ar[x]=st.nextToken().charAt(0);return ar;}char[][]
  arc(int n,int m)throws IOException {char ar[][]=new char[n][m];for(int x=0;x<n;x++){String s=bq.readLine();
      for(int y=0;y<m;y++)ar[x][y]=s.charAt(y);}return ar;}void p(int ar[])
  {StringBuilder sb=new StringBuilder
          (2*ar.length);for(int a:ar){sb.append(a);sb.append(' ');}out.println(sb);}void p(int ar[][])
  {StringBuilder sb=new StringBuilder(2*ar.length*ar[0].length);for(int a[]:ar){for(int aa:a){sb.append(aa);
      sb.append(' ');}sb.append("\n");}p(sb);}void p(long ar[]){StringBuilder sb=new StringBuilder
          (2*ar.length);for(long a:ar){ sb.append(a);sb.append(' ');}out.println(sb);}
      void p(long ar[][])
      {StringBuilder sb=new StringBuilder(2*ar.length*ar[0].length);for(long a[]:ar){for(long aa:a){sb.append(aa);
          sb.append(' ');}sb.append("\n");}p(sb);}void p(String ar[]){int c=0;for(String s:ar)c+=s.length()+1;
      StringBuilder sb=new StringBuilder(c);for(String a:ar){sb.append(a);sb.append(' ');}out.println(sb);}
      void p(double ar[])
      {StringBuilder sb=new StringBuilder(2*ar.length);for(double a:ar){sb.append(a);
          sb.append(' ');}out.println(sb);}void p
          (double ar[][]){StringBuilder sb=new StringBuilder(2*
          ar.length*ar[0].length);for(double a[]:ar){for(double aa:a){sb.append(aa);sb.append(' ');}sb.append("\n")
  ;}p(sb);}void p(char ar[])
  {StringBuilder sb=new StringBuilder(2*ar.length);for(char aa:ar){sb.append(aa);
      sb.append(' ');}out.println(sb);}void p(char ar[][]){StringBuilder sb=new StringBuilder(2*ar.length*ar[0]
          .length);for(char a[]:ar){for(char aa:a){sb.append(aa);sb.append(' ');}sb.append("\n");}p(sb);}
  }