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#include <cstdio>
#include <stdio.h>
#include <iostream>
#include <string>
#include <stdint.h>
#include <unordered_set>
#include <algorithm>
#include <vector>
#include <functional>


using namespace std;


static int32_t iN, iResult, iTime;

static uint32_t iInsideCase, iBorderCase;

static string sInput;

static vector<int32_t> vBorderCases;

static vector<int32_t> vInsideCases;

static bool fAllesKlar;


static void ReadData()
{
    cin >> iN >> sInput;
}


static void Init()
{
    vBorderCases.clear();
    vInsideCases.clear();

    fAllesKlar = false;

    bool f1stFinished = false;

    int i = 0;

    for (; i < iN; ++i)
    {
        if (sInput[i] == '1')
        {
            f1stFinished = true;
            break;
        }
    }

    if (!f1stFinished)
    {
        fAllesKlar = true;
        return;
    }

    if (i > 0)
        vBorderCases.push_back(i);

    bool fInOnes = true;
    int  iStartOfZeroes;

    for (; i < iN; ++i)
    {
        if (fInOnes)
        {
            if (sInput[i] == '1')
                continue;

            fInOnes = false;
            iStartOfZeroes = i;
            continue;
        }

        if (sInput[i] == '0')
            continue;

        vInsideCases.push_back(i - iStartOfZeroes);
        fInOnes = true;
    }

    if (!fInOnes)
        vBorderCases.push_back(iN - iStartOfZeroes);

    sort(vBorderCases.begin(), vBorderCases.end(), greater<int32_t>());

    if (vBorderCases.size() == 2 && vBorderCases[0] - vBorderCases[1] == 0)
    {
        vInsideCases.push_back(vBorderCases[0] + vBorderCases[1]);
        vBorderCases.clear();
    }

    sort(vInsideCases.begin(), vInsideCases.end(), greater<int32_t>());
}


static inline int32_t GetNext2Save()
{
    int32_t iRet;

    if (iInsideCase == vInsideCases.size())  // no more inside cases => we can take a border case
    {
        iRet = vBorderCases[iBorderCase++] - iTime++;

        if (iRet <= 0)
        {
            return 0;
        }

        return iRet;
    }

    if (iBorderCase == vBorderCases.size())  // no more border cases => we can take an inside case
    {
        iRet = vInsideCases[iInsideCase++] - (iTime++ * 2);

        if (iRet >= 3)
        {
            iTime++;
        }

        if (iRet >= 2)
        {
            iRet--;
        }

        if (iRet <= 0)
        {
            return 0;
        }

        return iRet;
    }

    int32_t i2SaveInBorderCase = vBorderCases[iBorderCase] - iTime;

    i2SaveInBorderCase = max(i2SaveInBorderCase, 0);

    int32_t i2SaveInInsideCase = vInsideCases[iInsideCase] - (iTime * 2);
    int32_t iInc = 1;

    if (i2SaveInInsideCase >= 3)
    {
        iInc++;
    }

    if (i2SaveInInsideCase >= 2)
    {
        i2SaveInInsideCase--;
    }

    i2SaveInInsideCase = max(i2SaveInInsideCase, 0);

    if (i2SaveInBorderCase >= i2SaveInInsideCase)
    {
        iTime++;
        iBorderCase++;
        return i2SaveInBorderCase;
    }

    iTime += iInc;
    iInsideCase++;
    return i2SaveInInsideCase;
}


static int32_t Solve()
{
    if (fAllesKlar)
    {
        return 0;
    }

    int32_t iSavedCities = 0;

    iInsideCase = 0;
    iBorderCase = 0;
    iTime = 0;

    while (iInsideCase < vInsideCases.size() || iBorderCase < vBorderCases.size())
    {
        int32_t iNext2Save = GetNext2Save();

        if (iNext2Save <= 0)
            break;

        iSavedCities += iNext2Save;
    }

    return iN - iSavedCities;
}


int main(int argc, char * argv[])
{
    int32_t iCnt, iResult;

    cin >> iCnt;

    for (int i = 0; i < iCnt; ++i)
    {
        ReadData();

        Init();

        iResult = Solve();

        cout << iResult;

        if (i < iCnt - 1)
        {
            cout << endl;
        }
    }

    return 0;
}