Naman has two binary strings s and t of length n (a binary string is a string which only consists of the characters "0" and "1"). He wants to convert s into t using the following operation as few times as possible.

In one operation, he can choose any subsequence of s and rotate it clockwise once.

For example, if s = 1110100, he can choose a subsequence corresponding to indices (1-based) \{2, 6, 7 \} and rotate them clockwise. The resulting string would then be s = 1010110.

A string a is said to be a subsequence of string b if a can be obtained from b by deleting some characters without changing the ordering of the remaining characters.

To perform a clockwise rotation on a sequence c of size k is to perform an operation which sets c_1:=c_k, c_2:=c_1, c_3:=c_2, …, c_k:=c_{k-1} simultaneously.

Determine the minimum number of operations Naman has to perform to convert s into t or say that it is impossible. 

Input

The first line contains a single integer n (1 ≤ n ≤ 10^6) — the length of the strings.

The second line contains the binary string s of length n.

The third line contains the binary string t of length n.

Output

If it is impossible to convert s to t after any number of operations, print -1.

Otherwise, print the minimum number of operations required.

Examples

Input


6
010000
000001


Output


1

Input


10
1111100000
0000011111


Output


5

Input


8
10101010
01010101


Output


1

Input


10
1111100000
1111100001


Output


-1

Note

In the first test, Naman can choose the subsequence corresponding to indices \{2, 6\} and rotate it once to convert s into t.

In the second test, he can rotate the subsequence corresponding to all indices 5 times. It can be proved, that it is the minimum required number of operations.

In the last test, it is impossible to convert s into t.
// Spaghetti code
import java.io.*;
import java.math.*;
import java.util.*;

public class Main {
    static PrintWriter pw;
    static class FastReader
    {
        private InputStream mIs;private byte[] buf = new byte[1024];private int curChar,numChars;public FastReader() { this(System.in); }public FastReader(InputStream is) { mIs = is;}
        public int read() {if (numChars == -1) throw new InputMismatchException();if (curChar >= numChars) {curChar = 0;try { numChars = mIs.read(buf);} catch (IOException e) { throw new InputMismatchException();}if (numChars <= 0) return -1; }return buf[curChar++];}
        public String nextLine(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isEndOfLine(c));return res.toString() ;}
        public String next(){int c = read();while (isSpaceChar(c)) c = read();StringBuilder res = new StringBuilder();do {res.appendCodePoint(c);c = read();}while (!isSpaceChar(c));return res.toString();}
        public long l(){int c = read();while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }long res = 0; do{ if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read();}while(!isSpaceChar(c));return res * sgn;}
        public int i(){int c = read() ;while (isSpaceChar(c)) c = read();int sgn = 1;if (c == '-') { sgn = -1 ; c = read() ; }int res = 0;do{if (c < '0' || c > '9') throw new InputMismatchException();res *= 10 ; res += c - '0' ; c = read() ;}while(!isSpaceChar(c));return res * sgn;}
        public double d() throws IOException {return Double.parseDouble(next()) ;}
        public boolean isSpaceChar(int c) { return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1; }
        public boolean isEndOfLine(int c) { return c == '\n' || c == '\r' || c == -1; }
        public void scanIntArr(int [] arr){ for(int li=0;li<arr.length;++li)arr[li]=i();}
        public void scanIntIndexArr(int [] arr){ for(int li=0;li<arr.length;++li){ arr[li]=i()-1;}}
        public void printIntArr(int [] arr){ for(int li=0;li<arr.length;++li)pw.print(arr[li]+" ");pw.println();}
        public void printLongArr(long [] arr){ for(int li=0;li<arr.length;++li)pw.print(arr[li]+" ");pw.println();}
        public void scanLongArr(long [] arr){for (int i=0;i<arr.length;++i){arr[i]=l();}}
        public void shuffle(int [] arr){ for(int i=arr.length;i>0;--i) { int r=(int)(Math.random()*i); int temp=arr[i-1]; arr[i-1]=arr[r]; arr[r]=temp; }}
        public int findMax(int [] arr){return Arrays.stream(arr).max().getAsInt();}

    }

    public static void main(String[] args) throws IOException {
        FastReader fr = new FastReader();
        pw = new PrintWriter(System.out);

     /*
inputCopy
6
010000
000001
outputCopy
1
inputCopy
10
1111100000
0000011111
outputCopy
5
inputCopy
8
10101010
01010101
outputCopy
1
inputCopy
10
1111100000
1111100001
outputCopy
-1

8
11001100
00110011

10
0110011001
1001100110

4
0110
1001

    */

        int t = 1;
        for (int ti = 0; ti < t; ++ti) {
            int n=fr.i();
            char [] strA=fr.nextLine().toCharArray();
            char [] strB=fr.nextLine().toCharArray();

            int cur=0,ans=0,oneA=0,oneB=0,max=0,min=0;
            for(int ni=0;ni<n;++ni){
                if(strA[ni]=='1')
                    ++oneA;
                if(strB[ni]=='1')
                    ++oneB;
                if(strA[ni]=='1'&&strB[ni]!='1')
                    ++cur;
                else if(strA[ni]=='0'&&strB[ni]!='0')
                    --cur;
                max=Math.max(max,cur);
                min=Math.min(min,cur);
            }
            if(oneA==oneB)
                pw.println(max-min);
            else
                pw.println(-1);
        }
        pw.flush();
        pw.close();
    }
}