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#include <iostream>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>

using namespace std;

class cmp {
public:
	bool operator()(pair<int, int> a, pair<int, int> b) {
		if (a.first == b.first) return a.second > b.second;
		return a.first < b.first;
	}
};

int main() {
	int z; cin >> z; while (z--) {
		int n; cin >> n;
		int in_1 = 0;

		string inp;
		cin >> inp;
		inp = "2" + inp + "2";
		int _1 = 0;
		priority_queue<int> Q2;
		priority_queue<int> Q1;
		pair<int, int> temp;
		vector<pair<int, int>> jedynka;
		for (int i = 1; i < n + 2; i++) {
			if (inp[i] == '0') {
				if (inp[i - 1] == '0') temp.first++;
				else temp = { 1,(int)(inp[i - 1] == '1') };
			}
			else {
				_1+=(inp[i]=='1');
				if (inp[i - 1] == '0') { temp.second += (int)(inp[i] == '1'); if (temp.second == 2) Q2.push(temp.first); else Q1.push(temp.first); }
			}
		}

		//cout << _1 << 'k';
		int dc = 0;
		while (!Q2.empty()) {
			if (Q1.empty() || Q1.top()+dc < Q2.top()) {
				int x = Q2.top(); Q2.pop();
				//cout << "(" << x << ",2)";
				_1 += min(x, 2 * dc + 1);
				dc += (int)(x >= 2 * dc + 1) + (int)(x > 2 * dc + 1);
				//cout << "[" << _1 << "/" << dc << "]";
			}
			else {
				int x = Q1.top(); Q1.pop();
				//cout << "(" << x << ",1)";
				_1 += min(x, dc);
				dc++; //cout << "[" << _1 << "/" << dc << "]";
			}
		}
		while (!Q1.empty()) {
			int x = Q1.top(); Q1.pop();
			//cout << "(" << x << ",1)";
			_1 += min(x, dc);
			dc++; //cout << "[" << _1 << "/" << dc << "]";
		}

		cout << _1 << endl;
	}
	return 0;
}