#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i = (a); i < (b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for(int i = (n) - 1; (i) >= 0; --i)
#define SZ(n) (int)(n).size()
#define ALL(n) (n).begin(), (n).end()
#define MOD LL(1e9 + 7)
#define INF 1000000
using namespace std;
typedef long long LL;
typedef vector<int> VI;
typedef pair<int, int> PI;

int main() {
	int d;
	cin >> d;
	char c[14];
	REP(i, 14) {
		cin >> c[i];
	}
	int ans = 0;
	REP(i, 14) {
		int sum = 0;
		int t = d;
		FOR(j, i, 14) {
			if (c[j] == 'x') {
				t--;
				if (t < 0) {
					break;
				}
			}
			sum++;
		}
		ans = max(ans, sum);
	}
	cout << ans << endl;
	return 0;
}