A

#include <bits/stdc++.h>
using namespace std;

int main() {
    int t;
    cin>>t;

    while(t--){
        int n;
        string s;
        cin>>n>>s;

        int a=0, b=0;

        int f=0;

        for(auto e: s)
        {
            if(f+'0' == e)
                f ^= 1;
            else
                a++;
        }

        f=1;

        for(auto e: s)
        {
            if(f+'0' == e)
                f ^= 1;
            else
                b++;
        }

        cout<<min(a, b)<<"\n";
    }
}