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#include <bits/stdc++.h>

using namespace std;

long long z;

vector<pair<long long, long long> > strefy;

bool por(pair<long long, long long> a, pair<long long, long long> b){
    if(a.first == b.first){
        if(a.second<b.second){
            return false;
        }
    }else{
        return a>b;
    }
}

void solve(){
    long long n;
    string s;
    cin>>n>>s;
    long long d = 0;
    bool l = false;
    if(s[0]=='1') l = true;
    for(char c : s){
        if(c=='1' && d!=0){
            if(l){
                strefy.push_back({d-1, d-1});
            }else{
                strefy.push_back({2*d, d});
                l = true;
            }
            d=0;
        }else if(c=='0'){
            d++;
        }
    }
    if(d!=0){
        strefy.push_back({2*d, d});
    }
    sort(strefy.begin(),strefy.end(), por);
    long long ruchy = 0, xd = 0;
    for(auto x : strefy){
        if(x.first == x.second){
            if(x.second-(ruchy*2)==0){
                n--;
                ruchy++;
            }else{
                n-=max(xd,x.second-(ruchy*2));
                ruchy+=2;
            }
        }else{
            n-=max(xd, x.second-ruchy);
            ruchy++;
        }
    }
    cout<<n<<"\n";

}



int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin>>z;
    for(int i = 0; i<z;i++){
        solve();
        strefy.clear();
    }
    return 0;
}