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#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

/*

3
8
00110100
10
1001000010
4
0000

1
19
1000001000001000001

1
20
00100000000100000010

1
20
00011000010100001000

1
20
00001111001001111000

*/

void solve(const int t, const string& s)
{
    vector<int> areas;
    vector<int> edgeAreas;
    int i=0;
    while(i<s.length())
    {
        int j=i+1;
        while(j<s.length()&&s[i]==s[j])++j;
        if(s[i]=='0')
        {
            bool isEdgeArea=i==0||j==s.length();
            (isEdgeArea?edgeAreas:areas).push_back(j-i);
        }
        i=j;
    }
    if(edgeAreas.size()==1&&edgeAreas[0]==s.length()&&areas.size()==0)
    {
        cout << 0 << endl;
        return;
    }
    int safeCityCount=0;
    int currentArea=0;
    sort(areas.begin(),areas.end(),greater<int>());
    int currentEdgeArea=0;
    sort(edgeAreas.begin(),edgeAreas.end(),greater<int>());
    int virusReach=0;
    while (true)
    {
        int edgeAreaSize=currentEdgeArea<edgeAreas.size()?(edgeAreas[currentEdgeArea]-virusReach):0;
        int areaSize=currentArea<areas.size()?(areas[currentArea]-virusReach*2):0;
	    if (edgeAreaSize*2>areaSize&&edgeAreaSize>0)
	    {
		    int savedCityCount = edgeAreas[currentEdgeArea++]-virusReach;
		    safeCityCount += savedCityCount;
		    ++virusReach;
	    }
        else if(areaSize>0)
        {
            int savedCityCount=areas[currentArea++]-virusReach*2;
            safeCityCount+=savedCityCount;
			++virusReach;
            if(savedCityCount>=2)
            {
                --safeCityCount;
                ++virusReach;
            }
        }
        else
            break;
    }
    cout<<(s.length()-safeCityCount)<<endl;
}

int main()
{
    int n;
    cin >> n;
    for(int i=0;i<n;++i)
    {
        int t;
        string s;
        cin >> t >> s;
        solve(t,s);
    }
    return 0;
}