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#define pb push_back
#define mp make_pair
#define fi first
#define se second 
#define all(...) begin(__VA_ARGS__) , end(__VA_ARGS__)
#define boost {ios_base::sync_with_stdio(false); cin.tie(); cout.tie();}

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef vector <int> vi;
typedef pair<int,int> PII;
typedef pair<ll,ll> PLL;
constexpr ll nax = 5e5+6969, INF = 2e9+6969;

int n;
void test_case()
{
	scanf("%d", &n);
	string S;
	cin >> S;
	vi A, B;
	bool First = 1;
	int cnt = 0;
	if(S[0] == '1') First = 0;
	for(int i=0;i<n;i++)
	{
		if(S[i] == '1')
		{
			if(cnt == 0) continue;
			if(First)
			{
				First = 0;
				A.pb(cnt);
			}
			else B.pb(cnt);
			cnt = 0;
			continue;
		}
		cnt++;
	}
	if(S[n - 1] == '0')
	{
		A.pb(cnt);
	}
	sort(all(B));
	sort(all(A));
	reverse(all(A));
	reverse(all(B));
	int pos = 0, ans = 0, rem = 0;
	for(int i=0;i<B.size();i++)
	{
		if(rem * 2 >= B[i]) continue;
		B[i] -= rem * 2;
		while(pos < A.size())
		{
			if(A[pos] <= rem)
			{
				pos++;
				continue;
			}
			if(B[i] == 1)
			{
				B[i] = 0;
				ans+=A[pos]-rem;
				pos++;
				rem++;
				break;
			}
			else if(B[i] == 2)
			{
				B[i] = 0;
				ans+=A[pos]-rem;
				pos++;
				rem++;
				break;
			}
			else if(B[i] == 3)
			{
				ans += A[pos] + 1-rem;
				rem += 2;
				B[i] = 0;
				pos++;
				break;
			}
			else if(B[i] == 4)
			{
				ans += A[pos] + 2-rem;
				pos++;
				rem += 3;
				B[i] = 0;
				break;
			}
			else
			{
				ans += A[pos] - rem;
				rem++;
				B[i] -= 2;
				pos++;
			}
		}
		if(B[i] > 0) 
		{
			ans += max(1, B[i] - 1);
			if(B[i] == 1) rem++;
			else rem += 2;
		}
	}
	while(pos < A.size())
	{
		if(rem >= A[pos])
		{
			pos++;
			continue;
		}
		ans += A[pos] - rem;
		rem++;
		pos++;
	}
	
	printf("%d\n", n - ans);
}

int main()
{
	int qq;
	scanf("%d", &qq);
	while(qq--) test_case();
	
	return 0;
}