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#include <iostream>
#include <queue>

void one() {
    int n;
    std::cin >> n;

    bool first = true;
    int left = 0;
    int right = 0;
    std::priority_queue<int> two_bag;

    for (int i = 0; i < n; ++i) {
        char c;
        std::cin >> c;
        if (c == '0') {
            if (first) {
                left += 1;
            } else {
                right += 1;
            }
        } else {
            if (first) {
                first = false;
            } else {
                two_bag.push(right);
                right = 0;
            }
        }
    }

    if (first) {
        std::cout << "0\n";
        return;
    }

    int safe = 0;
    std::priority_queue<int> one_bag;
    one_bag.push(left);
    one_bag.push(right);

    for (int it = 0; ; ++it) {
        int two_top = two_bag.empty() ? -1 : two_bag.top() - 2 * it;
        int one_top = one_bag.empty() ? -1 : one_bag.top() - it;
        if (two_top > 0 && two_top >= one_top * 2) {
            safe += 1;
            two_bag.pop();
            one_bag.push(two_top + it - 1);
        } else if (one_top > 0) {
            safe += one_top;
            one_bag.pop();
        } else {
            break;
        }
    }

    std::cout << n - safe << "\n";
}

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

    for (int i = 0; i < t; ++i) {
        one();
    }
}