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.BufferedReader;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.*;
import java.io.*;
public class Main {
    // Graph
    // prefix sums
    //inputs
    public static void main(String args[])throws Exception{
        Input sc=new Input();
        precalculates p=new precalculates();
        StringBuilder sb=new StringBuilder();
        int t=sc.readInt();
        for(int f=0;f<t;f++){
            int n=sc.readInt();
            String str1=sc.readString();
            String str2=sc.readString();
            int count=0;
            int a,b;
            a=0;b=0;
            boolean bb=true;
            for(int i=0;i<n;i++){
                if(str1.charAt(i)=='1')
                    count++;
                if(str1.charAt(i)!= str2.charAt(i)){
                    bb=false;
                    a++;
                }else{
                    b++;
                }
            }
            if(bb){
                sb.append("0\n");
            }else{
                if(count>0){
                    sb.append(Math.min(a,b)+"\n");
                }else{
                    sb.append("-1\n");
                }
            }
        }
        System.out.print(sb);
    }
    /*

    101101100
    ---------
    100010111
    ---------
    111101000
    001010111
    110101100




     */
}
class Input{
    BufferedReader br;
    StringTokenizer st;
    Input(){
        br=new BufferedReader(new InputStreamReader(System.in));
        st=new StringTokenizer("");
    }
    public int[] readArray() throws Exception{
        st=new StringTokenizer(br.readLine());
        int a[]=new int[st.countTokens()];
        for(int i=0;i<a.length;i++){
            a[i]=Integer.parseInt(st.nextToken());
        }
        return a;
    }
    public long[] readArrayLong() throws Exception{
        st=new StringTokenizer(br.readLine());
        long a[]=new long[st.countTokens()];
        for(int i=0;i<a.length;i++){
            a[i]=Long.parseLong(st.nextToken());
        }
        return a;
    }
    public int readInt() throws Exception{
        st=new StringTokenizer(br.readLine());
        return Integer.parseInt(st.nextToken());
    }
    public long readLong() throws Exception{
        st=new StringTokenizer(br.readLine());
        return Long.parseLong(st.nextToken());
    }
    public String readString() throws Exception{
        return br.readLine();
    }
    public int[][] read2dArray(int n,int m)throws Exception{
        int a[][]=new int[n][m];
        for(int i=0;i<n;i++){
            st=new StringTokenizer(br.readLine());
            for(int j=0;j<m;j++){
                a[i][j]=Integer.parseInt(st.nextToken());
            }
        }
        return a;
    }
}
class precalculates{
    public long gcd(long p, long q) {
        if (q == 0) return p;
        else return gcd(q, p % q);
    }
    public int[] prefixSumOneDimentional(int a[]){
        int n=a.length;
        int dp[]=new int[n];
        for(int i=0;i<n;i++){
            if(i==0)
                dp[i]=a[i];
            else
                dp[i]=dp[i-1]+a[i];
        }
        return dp;
    }
    public int[] postSumOneDimentional(int a[]) {
        int n = a.length;
        int dp[] = new int[n];
        for (int i = n - 1; i >= 0; i--) {
            if (i == n - 1)
                dp[i] = a[i];
            else
                dp[i] = dp[i + 1] + a[i];
        }
        return dp;
    }
    public int[][] prefixSum2d(int a[][]){
        int n=a.length;int m=a[0].length;
        int dp[][]=new int[n+1][m+1];
        for(int i=1;i<=n;i++){
            for(int j=1;j<=m;j++){
                dp[i][j]=a[i-1][j-1]+dp[i-1][j]+dp[i][j-1]-dp[i-1][j-1];
            }
        }
        return dp;
    }
    public long pow(long a,long b){
        long mod=1000000007;
        long ans=1;
        if(b<=0)
            return 1;
        if(b%2==0){
            ans=pow(a,b/2)%mod;
            return ((ans%mod)*(ans%mod))%mod;
        }else{
            ans=pow(a,b-1)%mod;
            return ((a%mod)*(ans%mod))%mod;
        }
    }

}
class GraphInteger{
    HashMap<Integer,vertex> vtces;
    class vertex{
        HashMap<Integer,Integer> children;
        public vertex(){
            children=new HashMap<>();
        }
    }
    public GraphInteger(){
        vtces=new HashMap<>();
    }
    public void addVertex(int a){
        vtces.put(a,new vertex());
    }
    public void addEdge(int a,int b,int cost){
        if(!vtces.containsKey(a)){
            vtces.put(a,new vertex());
        }
        if(!vtces.containsKey(b)){
            vtces.put(b,new vertex());
        }
        vtces.get(a).children.put(b,cost);
//        vtces.get(b).children.put(a,cost);
    }
    public boolean isCyclicDirected(){
        boolean isdone[]=new boolean[vtces.size()+1];
        boolean check[]=new boolean[vtces.size()+1];
        for(int i=1;i<=vtces.size();i++) {
            if (!isdone[i] && isCyclicDirected(i,isdone, check)) {
                return true;
            }
        }
        return false;
    }
    private boolean isCyclicDirected(int i,boolean isdone[],boolean check[]){
        if(check[i])
            return true;
        if(isdone[i])
            return false;
        check[i]=true;
        isdone[i]=true;
        Set<Integer> set=vtces.get(i).children.keySet();
        for(Integer ii:set){
            if(isCyclicDirected(ii,isdone,check))
                return true;
        }
        check[i]=false;
        return false;
    }
}
class union_find {
    int n;
    int[] sz;
    int[] par;

    union_find(int nval) {
        n = nval;
        sz = new int[n + 1];
        par = new int[n + 1];
        for (int i = 0; i <= n; i++) {
            par[i] = i;
            sz[i] = 1;
        }
    }

    int root(int x) {
        if (par[x] == x)
            return x;
        return par[x] = root(par[x]);
    }

    boolean find(int a, int b) {
        return root(a) == root(b);
    }

    int union(int a, int b) {
        int ra = root(a);
        int rb = root(b);
        if (ra == rb)
            return 0;
        if(a==b)
            return 0;
        if (sz[a] > sz[b]) {
            int temp = ra;
            ra = rb;
            rb = temp;
        }
        par[ra] = rb;
        sz[rb] += sz[ra];
        return 1;
    }
}







