#include<bits/stdc++.h>

using namespace std;

const int N=1e6;

string a,b;

int p[26];

int t;

int n,m;

void solve(string s)

{

int num=0;

for(int i=0;i<n+m;i++)

{

int j=s[i]-'a';

p[j]++;

}

for(int i=0;i<26;i++)if(p[i]%2==1)num++;

if((n+m)%2==0)cout<<num/2<<endl;

else

{

if(num==1)cout<<num<<endl;

else cout<<(num-1)/2<<endl;

}

}

int main()

{

cin>>t;

while(t--)

{

cin>>n>>m;

cin>>a>>b;

string s=a+b;

solve(s);

memset(p,0,sizeof p);

}

return 0;

}