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.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.math.BigInteger;
  import java.text.DecimalFormat;
  import java.util.*;
  import java.util.concurrent.ThreadLocalRandom;
  import java.util.stream.Collectors;
  import java.util.stream.IntStream;
  import java.util.stream.LongStream;
  
  public class TaskD {
  
      static long mod = 1000000007;
      static FastScanner scanner;
  
      static final StringBuilder result = new StringBuilder();
  
      public static void main(String[] args) {
          scanner = new FastScanner();
          int T = scanner.nextInt();
          for (int t = 0; t < T; t++) {
              solve();
          }
          System.out.println(result);
      }
  
      static List<WithIdx>[] graph;
  
      static void solve() {
          int n = scanner.nextInt();
          int m = scanner.nextInt();
          graph = new List[n];
          for (int i = 0; i < n; i++) graph[i] = new ArrayList<>();
          for (int i = 0; i < m; i++) {
              int a = scanner.nextInt() - 1;
              int b = scanner.nextInt() - 1;
              String data = scanner.nextToken();
              graph[a].add(new WithIdx(b, data.equals("crewmate") ? 1 : -1));
              graph[b].add(new WithIdx(a, data.equals("crewmate") ? 1 : -1));
          }
          int[] vis1 = new int[n];
          int[] vis2 = new int[n];
  
          int res = 0;
          for (int i = 0; i < n; i++) {
              if (vis1[i] != 0) continue;
              int current = Math.max(dfs(i, 1, vis1), dfs(i, -1, vis2));
              if (current == -1) {
                  result.append(-1).append("\n");
                  return;
              }
              res += current;
          }
          result.append(res).append("\n");
      }
  
      static int dfs(int current, int score, int[] visited) {
          if (visited[current] != 0) {
              return visited[current] == score ? 0 : -1;
          }
          visited[current] = score;
          int sum = score == -1 ? 1 : 0;
          for (WithIdx child : graph[current]) {
              int childRes = dfs(child.val, child.idx * score, visited);
              if (childRes == -1) {
                  return -1;
              }
              sum += childRes;
          }
          return sum;
      }
  
      static class WithIdx implements Comparable<WithIdx> {
          int val, idx;
  
          public WithIdx(int val, int idx) {
              this.val = val;
              this.idx = idx;
          }
  
          @Override
          public int compareTo(WithIdx o) {
              if (val == o.val) {
                  return Integer.compare(idx, o.idx);
              }
              return Integer.compare(val, o.val);
          }
      }
  
      public static class FastScanner {
          BufferedReader br;
          StringTokenizer st;
  
          public FastScanner() {
              br = new BufferedReader(new InputStreamReader(System.in));
          }
  
          String nextToken() {
              while (st == null || !st.hasMoreElements()) {
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      // TODO Auto-generated catch block
                      e.printStackTrace();
                  }
              }
              return st.nextToken();
          }
  
          String nextLine() {
              try {
                  return br.readLine();
              } catch (Exception e) {
                  e.printStackTrace();
                  throw new RuntimeException();
              }
          }
  
          int nextInt() {
              return Integer.parseInt(nextToken());
          }
  
          long nextLong() {
              return Long.parseLong(nextToken());
          }
  
          double nextDouble() {
              return Double.parseDouble(nextToken());
          }
  
          int[] nextIntArray(int n) {
              int[] res = new int[n];
              for (int i = 0; i < n; i++) res[i] = nextInt();
              return res;
          }
  
          long[] nextLongArray(int n) {
              long[] res = new long[n];
              for (int i = 0; i < n; i++) res[i] = nextLong();
              return res;
          }
  
          String[] nextStringArray(int n) {
              String[] res = new String[n];
              for (int i = 0; i < n; i++) res[i] = nextToken();
              return res;
          }
      }
  
      static class PrefixSums {
          long[] sums;
  
          public PrefixSums(long[] sums) {
              this.sums = sums;
          }
  
          public long sum(int fromInclusive, int toExclusive) {
              if (fromInclusive > toExclusive) throw new IllegalArgumentException("Wrong value");
              return sums[toExclusive] - sums[fromInclusive];
          }
  
          public static PrefixSums of(int[] ar) {
              long[] sums = new long[ar.length + 1];
              for (int i = 1; i <= ar.length; i++) {
                  sums[i] = sums[i - 1] + ar[i - 1];
              }
              return new PrefixSums(sums);
          }
  
          public static PrefixSums of(long[] ar) {
              long[] sums = new long[ar.length + 1];
              for (int i = 1; i <= ar.length; i++) {
                  sums[i] = sums[i - 1] + ar[i - 1];
              }
              return new PrefixSums(sums);
          }
      }
  
      static class ADUtils {
          static void sort(int[] ar) {
              Random rnd = ThreadLocalRandom.current();
              for (int i = ar.length - 1; i > 0; i--) {
                  int index = rnd.nextInt(i + 1);
                  // Simple swap
                  int a = ar[index];
                  ar[index] = ar[i];
                  ar[i] = a;
              }
              Arrays.sort(ar);
          }
  
          static void reverse(int[] arr) {
              int last = arr.length / 2;
              for (int i = 0; i < last; i++) {
                  int tmp = arr[i];
                  arr[i] = arr[arr.length - 1 - i];
                  arr[arr.length - 1 - i] = tmp;
              }
          }
  
          static void sort(long[] ar) {
              Random rnd = ThreadLocalRandom.current();
              for (int i = ar.length - 1; i > 0; i--) {
                  int index = rnd.nextInt(i + 1);
                  // Simple swap
                  long a = ar[index];
                  ar[index] = ar[i];
                  ar[i] = a;
              }
              Arrays.sort(ar);
          }
      }
  
      static class MathUtils {
          static long[] FIRST_PRIMES = {
                  2, 3, 5, 7, 11, 13, 17, 19, 23, 29,
                  31, 37, 41, 43, 47, 53, 59, 61, 67, 71,
                  73, 79, 83, 89, 97, 101, 103, 107, 109, 113,
                  127, 131, 137, 139, 149, 151, 157, 163, 167, 173,
                  179, 181, 191, 193, 197, 199, 211, 223, 227, 229,
                  233, 239, 241, 251, 257, 263, 269, 271, 277, 281,
                  283, 293, 307, 311, 313, 317, 331, 337, 347, 349,
                  353, 359, 367, 373, 379, 383, 389, 397, 401, 409,
                  419, 421, 431, 433, 439, 443, 449, 457, 461, 463,
                  467, 479, 487, 491, 499, 503, 509, 521, 523, 541,
                  547, 557, 563, 569, 571, 577, 587, 593, 599, 601,
                  607, 613, 617, 619, 631, 641, 643, 647, 653, 659,
                  661, 673, 677, 683, 691, 701, 709, 719, 727, 733,
                  739, 743, 751, 757, 761, 769, 773, 787, 797, 809,
                  811, 821, 823, 827, 829, 839, 853, 857, 859, 863,
                  877, 881, 883, 887, 907, 911, 919, 929, 937, 941,
                  947, 953, 967, 971, 977, 983, 991, 997, 1009, 1013,
                  1019, 1021, 1031, 1033, 1039, 1049, 1051};
  
          static long[] primes(int to) {
              long[] all = new long[to + 1];
              long[] primes = new long[to + 1];
              all[1] = 1;
              int primesLength = 0;
              for (int i = 2; i <= to; i++) {
                  if (all[i] == 0) {
                      primes[primesLength++] = i;
                      all[i] = i;
                  }
                  for (int j = 0; j < primesLength && i * primes[j] <= to && all[i] >= primes[j];
                          j++) {
                      all[(int) (i * primes[j])] = primes[j];
                  }
              }
              return Arrays.copyOf(primes, primesLength);
          }
  
          static long modpow(long b, long e, long m) {
              long result = 1;
  
              while (e > 0) {
                  if ((e & 1) == 1) {
                      /* multiply in this bit's contribution while using modulus to keep
                       * result small */
                      result = (result * b) % m;
                  }
                  b = (b * b) % m;
                  e >>= 1;
              }
  
              return result;
          }
  
          static long submod(long x, long y, long m) {
              return (x - y + m) % m;
          }
  
          static long modInverse(long a, long m) {
              long g = gcdF(a, m);
              if (g != 1) {
                  throw new IllegalArgumentException("Inverse doesn't exist");
              } else {
                  // If a and m are relatively prime, then modulo
                  // inverse is a^(m-2) mode m
                  return modpow(a, m - 2, m);
              }
          }
  
          static public long gcdF(long a, long b) {
              while (b != 0) {
                  long na = b;
                  long nb = a % b;
                  a = na;
                  b = nb;
              }
              return a;
          }
      }
  }
  
  /*
  5
  3 2 3 8 8
  2 8 5 10 1
  
   */