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#include <bits/stdc++.h>

using namespace std;

int main()
{
    int t = 0;
    cin >> t;
    for (int p = 0; p < t; ++p)
    {
        int n;
        cin >> n;

        vector<int> prze;

        int licz = 0;

        string inp;
        int l = -1, pp = -1;
        priority_queue<int> q;
        cin >> inp;
        int las = inp[0] - '0';
        int zam = 0;
        for (int i = 0; i < n; ++i)
        {

            int pom = inp[i] - '0';
            if (pom != las)
            {
                zam++;
                if (pom == 1)
                {

                    if (zam > 1)
                    {
                        prze.push_back(licz);
                        q.push(licz);
                    }
                    else if (zam == 1)
                        l = licz;
                }
                licz = 0;
            }
            licz++;
            las = pom;
        }
        if (las == 0)
            pp = licz;

        int w = 0;
        int ep = 0;
        while (!q.empty() or l > 0 or pp > 0)
        {
            int top = 0;
            if (q.empty())
                top = 0;
            else
                top = q.top();

            int f = max(l,0)+max(pp,0);
            if (pp > 0 and l > 0)
            f--;
            if (top-1-ep*2 <= f and (pp > 0 or l >0))
            {
                if (l > pp)
                {
                    w += l;
                    l = -1;
                    ep++;
                    l--;
                    pp--;
                }
                else
                {
                    w += pp;
                    pp = -1;
                    ep++;
                    l--;
                    pp--;
                }
            }
            else
            {
                if (ep == 0 and top == 1)
                {
                    w += 1;
                    ep++;
                    l--;
                    pp--;
                    l--;
                    pp--;
                }
                if (top - 1 - ep * 2 < 1 and top-ep*2 != 1)
                {
                    q.pop();
                    continue;
                }

                if (top - ep*2 == 1)
                w+=1;
                else
                w += top - 1 - ep * 2;
                q.pop();
                ep++;
                ep++;
                l--;
                pp--;
                l--;
                pp--;
            }
        }
        int z = n - w;
        cout << z << endl;
    }
}

/*

3
8
00110100
10
1001000010
4
0000

1
10
1001000010

1
4
0000

1
69
010100100010000001001000001000100010000000000000000000000000000000011


1
20
00011000000000001000


1
20
11111111111111010111


1
20
11010001110110111100

1
20
00010100001100000000

1
20
00010000010100101000


1
15
001100000011000
9
*/