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#include <bits/stdc++.h>
 
#define INF 2147483647
#define LINF 9223372036854775807
#define NINF -2147483648
#define NLINF -9223372036854775808
#define M 1000000007
#define M1 998244353
#define A 26
#define K 31
#define P 2137
 
using namespace std;
using db=double;
using dbl=long double;
using ll=long long;
using pi=pair<int,int>;
using pl=pair<ll,ll>;
using vi=vector<int>;
using vl=vector<ll>;
using gr=vector<vector<int> >;
using grl=vector<vector<ll> >;

 
#define fp(x, a, b) for (int (x) = (a); (x) < (b); (x)++)
#define f(x, n) for (int (x) = 0; (x) < (n); (x)++)
#define fnp(x, a, b) for (int (x) = (b) - 1; (x) >= (a); (x)--)
#define fn(x, n) for (int (x) = (n - 1); (x) >= 0; (x)--)
#define sgn(x) (x) > 0 ? 1 : (x) == 0 ? 0 : -1
#define gcd(a, b) __gcd((a), (b))
#define lcm(a, b) (a) * (b) / gcd((a), (b))
#define x first
#define y second
#define mp make_pair 
#define pb push_back
#define s(x) x.size()
#define all(x) x.begin(), x.end()
#define ans(x) cout<<(x)<<"\n"
#define yes printf("YES\n")
#define no printf("NO\n")
#define fl cout.flush()
#define debarr(x, n) f(i, (n)){cout<<(x)[i]<<" ";}cout<<"\n"
#define debgr(x, n) f(i, (n)){f(j, s((x)[i])){cout<<(x)[i][j]<<" ";}cout<<"\n";}

 
mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());


 
void input();
void compute();
 
int main()
{
	int T = 1;
	scanf("%d", &T);
	while(T--)
	{
		input();
		compute();
	}
	return 0;
}

#define N 
 
ll n;
string s;
ll w;
ll p;
int r;
pair<int, pi> t;
priority_queue<pair<int, pi> > pq[2];
vector<pi> v;

void input()
{
	cin >> n >> s;
	w = 0;
	while(!pq[0].empty())
		pq[0].pop();
	while(!pq[1].empty())
		pq[1].pop();
	v.clear();
	p = -1;
}
void compute()
{
	f(i, n)
	{
		if(s[i] == '1')
		{
			if(i - p - 1 > 0)
			{
				v.pb(mp(i - p - 1, 2));
			}
			p = i;
		}	
	}
	if(n - p - 1 > 0)
	{
		v.pb(mp(n - p - 1, 2));
	}
	if(s[0] == '0')
		v[0].y--;
	if(s[n - 1] == '0')
		v[s(v) - 1].y--;
	f(i, s(v))
	{
		//cout<<v[i].x<<" "<<v[i].y<<"k\n";
		if(v[i].y == 0)
		{
			cout<<0<<"\n";
			return;
		}
		pq[0].push(mp(v[i].x * (v[i].y == 1 ? 2 : 1), mp(-v[i].y, v[i].x)));
	}
	while(!pq[0].empty())
	{
		t = pq[0].top();
		pq[0].pop();
		t.y.x *= -1;
		if(t.y.x == 0)
		{
			w += t.y.y;
		}
		else if(t.y.x == 1)
		{
			w += t.y.y;
			t.y.x--;
		}
		else
		{
			t.y.x--;
			w++;
		}
		t.y.y -= t.y.x + 1;
		if(t.y.y > 0 && t.y.x > 0)
		{
			t.y.x *= -1;
			pq[1].push(mp(t.y.y * (-t.y.x == 1 ? 2 : 1), mp(t.y.x, t.y.y)));
		}
		while(!pq[0].empty())
		{
			t = pq[0].top();
			pq[0].pop();
			t.y.x *= -1;
			t.y.y -= t.y.x;
			if(t.y.y > 0)
			{
				t.y.x *= -1;
				pq[1].push(mp(t.y.y * (-t.y.x == 1 ? 2 : 1), mp(t.y.x, t.y.y)));
			}
		}
		swap(pq[0], pq[1]);
	}
	cout<<n - w<<"\n";
}