There are n candles on a Hanukkah menorah, and some of its candles are initially lit. We can describe which candles are lit with a binary string s, where the i-th candle is lit if and only if s_i=1.

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Initially, the candle lights are described by a string a. In an operation, you select a candle that is currently lit. By doing so, the candle you selected will remain lit, and every other candle will change (if it was lit, it will become unlit and if it was unlit, it will become lit).

You would like to make the candles look the same as string b. Your task is to determine if it is possible, and if it is, find the minimum number of operations required.

Input

The first line contains an integer t (1≤ t≤ 10^4) — the number of test cases. Then t cases follow.

The first line of each test case contains a single integer n (1≤ n≤ 10^5) — the number of candles.

The second line contains a string a of length n consisting of symbols 0 and 1 — the initial pattern of lights.

The third line contains a string b of length n consisting of symbols 0 and 1 — the desired pattern of lights.

It is guaranteed that the sum of n does not exceed 10^5.

Output

For each test case, output the minimum number of operations required to transform a to b, or -1 if it's impossible.

Example

Input


5
5
11010
11010
2
01
11
3
000
101
9
100010111
101101100
9
001011011
011010101


Output


0
1
-1
3
4

Note

In the first test case, the two strings are already equal, so we don't have to perform any operations.

In the second test case, we can perform a single operation selecting the second candle to transform 01 into 11.

In the third test case, it's impossible to perform any operations because there are no lit candles to select.

In the fourth test case, we can perform the following operations to transform a into b: 

  1. Select the 7-th candle: 100010{\color{red}1}11→ 011101{\color{red} 1}00. 
  2. Select the 2-nd candle: 0{\color{red} 1}1101100→ 1{\color{red} 1}0010011. 
  3. Select the 1-st candle: {\color{red}1}10010011→ {\color{red}1}01101100. 



In the fifth test case, we can perform the following operations to transform a into b: 

  1. Select the 6-th candle: 00101{\color{red}1}011→ 11010{\color{red}1}100 
  2. Select the 2-nd candle: 1{\color{red}1}0101100→ 0{\color{red}1}1010011 
  3. Select the 8-th candle: 0110100{\color{red}1}1→ 1001011{\color{red}1}0 
  4. Select the 7-th candle: 100101{\color{red}1}10→ 011010{\color{red}1}01 
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.math.BigInteger;
import java.util.*;

/**
 * @author Mubtasim Shahriar
 */

public class Cgr18A {


    public static void main(String[] args) {

        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader sc = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        Solver solver = new Solver();
        int t = sc.nextInt();
//        int t = 1;
        while (t-- != 0) {
            solver.solve(sc, out);
        }
        out.close();

    }

    static class Solver {
        final int INF = (int) 1e9;
        public void solve(InputReader sc, PrintWriter out) {
            int n = sc.nextInt();
            char[] a = sc.next().toCharArray();
            char[] b = sc.next().toCharArray();
            boolean isAllZeroA = isAllZero(a);
            boolean isAllZeroB = isAllZero(b);
            if(isAllZeroA && isAllZeroB) {
                out.println(0);
                return;
            }
            if(isAllZeroA || isAllZeroB) {
                out.println(-1);
                return;
            }
            int eq = 0;
            for(int i = 0; i< n;i++) if(a[i]==b[i]) eq++;
            int eqHasOne = 0;
            int notEqHasOne = 0;
            int noteq = n-eq;
            for (int i = 0; i < n; i++) {
                if(a[i]==b[i] && a[i]=='1') eqHasOne++;
                if(a[i]!=b[i] && a[i]=='1') notEqHasOne++;
            }
            int l = solveIt(new int[] {eq,noteq},new int[] {eqHasOne,notEqHasOne},0);
            int r = solveIt(new int[] {eq,noteq},new int[] {eqHasOne,notEqHasOne},1);
            if(l==INF && r==INF) {
                out.println(-1);
            } else {
                out.println(Math.min(l,r));
            }
        }

        private boolean isAllZero(char[] a) {
            for(char c : a) if(c=='1') return false;
            return true;
        }

        private int solveIt(int[] arr,int[] hasOne, int minusPointer) {
            if(arr[0]==0 && arr[1]==0) throw new RuntimeException();
            int cnt = 0;
            int max = arr[0] + arr[1];
            while(arr[1]!=0) {
                int minus = minusPointer;
                int plus = 1-minus;
                if(hasOne[minusPointer]<1) return INF;
                int eqHasOne = hasOne[0];
                int notEqHasOne = hasOne[1];
                int eqHasZero = arr[0] - eqHasOne;
                int notEqHasZero = arr[1] - notEqHasOne;
                if(minusPointer==0) {
                    int newNotEqHasOne = eqHasZero;
                    int newEqHasOne = notEqHasZero + 1;
                    hasOne[0] = newEqHasOne;
                    hasOne[1] = newNotEqHasOne;
                } else {
                    int newEqHasOne = notEqHasZero;
                    int newNotEqHasOne = eqHasZero + 1;
                    hasOne[0] = newEqHasOne;
                    hasOne[1] = newNotEqHasOne;
                }
                int minusValue = arr[minus]-1;
                int plusValue = arr[plus]+1;
                arr[minus] = plusValue;
                arr[plus] = minusValue;
                minusPointer = 1-minusPointer;
                cnt++;
                if(cnt>max+10) break;
            }
            if(arr[1]!=0) return INF;
            return cnt;
        }
    }

    static void sort(int[] arr) {
        ArrayList<Integer> al = new ArrayList();
        for (int i : arr) al.add(i);
        Collections.sort(al);
        int idx = 0;
        for (int i : al) arr[idx++] = i;
    }

    static void sort(long[] arr) {
        ArrayList<Long> al = new ArrayList();
        for (long i : arr) al.add(i);
        Collections.sort(al);
        int idx = 0;
        for (long i : al) arr[idx++] = i;
    }

    static void sortDec(int[] arr) {
        ArrayList<Integer> al = new ArrayList();
        for (int i : arr) al.add(i);
        Collections.sort(al, Collections.reverseOrder());
        int idx = 0;
        for (int i : al) arr[idx++] = i;
    }

    static void sortDec(long[] arr) {
        ArrayList<Long> al = new ArrayList();
        for (long i : arr) al.add(i);
        Collections.sort(al, Collections.reverseOrder());
        int idx = 0;
        for (long i : al) arr[idx++] = i;
    }

    static class InputReader {
        private boolean finished = false;

        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;

        public InputReader(InputStream stream) {
            this.stream = stream;
        }

        public int read() {
            if (numChars == -1) {
                throw new InputMismatchException();
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    throw new InputMismatchException();
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar++];
        }

        public int peek() {
            if (numChars == -1) {
                return -1;
            }
            if (curChar >= numChars) {
                curChar = 0;
                try {
                    numChars = stream.read(buf);
                } catch (IOException e) {
                    return -1;
                }
                if (numChars <= 0) {
                    return -1;
                }
            }
            return buf[curChar];
        }

        public int nextInt() {
            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 long nextLong() {
            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 String nextString() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            StringBuilder res = new StringBuilder();
            do {
                if (Character.isValidCodePoint(c)) {
                    res.appendCodePoint(c);
                }
                c = read();
            } while (!isSpaceChar(c));
            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null) {
                return filter.isSpaceChar(c);
            }
            return isWhitespace(c);
        }

        public static boolean isWhitespace(int c) {
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        private String readLine0() {
            StringBuilder buf = new StringBuilder();
            int c = read();
            while (c != '\n' && c != -1) {
                if (c != '\r') {
                    buf.appendCodePoint(c);
                }
                c = read();
            }
            return buf.toString();
        }

        public String readLine() {
            String s = readLine0();
            while (s.trim().length() == 0) {
                s = readLine0();
            }
            return s;
        }

        public String readLine(boolean ignoreEmptyLines) {
            if (ignoreEmptyLines) {
                return readLine();
            } else {
                return readLine0();
            }
        }

        public BigInteger readBigInteger() {
            try {
                return new BigInteger(nextString());
            } catch (NumberFormatException e) {
                throw new InputMismatchException();
            }
        }

        public char nextCharacter() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            return (char) c;
        }

        public double nextDouble() {
            int c = read();
            while (isSpaceChar(c)) {
                c = read();
            }
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E') {
                    return res * Math.pow(10, nextInt());
                }
                if (c < '0' || c > '9') {
                    throw new InputMismatchException();
                }
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c)) {
                    if (c == 'e' || c == 'E') {
                        return res * Math.pow(10, nextInt());
                    }
                    if (c < '0' || c > '9') {
                        throw new InputMismatchException();
                    }
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }

        public boolean isExhausted() {
            int value;
            while (isSpaceChar(value = peek()) && value != -1) {
                read();
            }
            return value == -1;
        }

        public String next() {
            return nextString();
        }

        public SpaceCharFilter getFilter() {
            return filter;
        }

        public void setFilter(SpaceCharFilter filter) {
            this.filter = filter;
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }

        public int[] nextIntArray(int n) {
            int[] array = new int[n];
            for (int i = 0; i < n; ++i) array[i] = nextInt();
            return array;
        }

        public int[] nextSortedIntArray(int n) {
            int array[] = nextIntArray(n);
            Arrays.sort(array);
            return array;
        }

        public int[] nextSumIntArray(int n) {
            int[] array = new int[n];
            array[0] = nextInt();
            for (int i = 1; i < n; ++i) array[i] = array[i - 1] + nextInt();
            return array;
        }

        public long[] nextLongArray(int n) {
            long[] array = new long[n];
            for (int i = 0; i < n; ++i) array[i] = nextLong();
            return array;
        }

        public long[] nextSumLongArray(int n) {
            long[] array = new long[n];
            array[0] = nextInt();
            for (int i = 1; i < n; ++i) array[i] = array[i - 1] + nextInt();
            return array;
        }

        public long[] nextSortedLongArray(int n) {
            long array[] = nextLongArray(n);
            Arrays.sort(array);
            return array;
        }
    }


}
