#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cstring>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <numeric>
#include <cctype>
#include <tuple>
#include <array>
#include <climits>
#include <bitset>
#include <cassert>

#ifdef _MSC_VER
#include <agents.h>
#endif

#define FOR(i, a, b) for(int i = (a); i < (int)(b); ++i)
#define rep(i, n) FOR(i, 0, n)
#define ALL(v) v.begin(), v.end()
#define REV(v) v.rbegin(), v.rend()
#define MEMSET(v, s) memset(v, s, sizeof(v))
#define UNIQUE(v) (v).erase(unique(ALL(v)), (v).end())
#define MP make_pair
#define MT make_tuple

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> P;

const string yuki = "yuki";
int check(int i, int x, vector<int> cnt){
	if (i == 4) return x <= accumulate(ALL(cnt), 0);

	for (int ch = yuki[i] + 1; ch <= 'z'; ++ch){
		int num = min(x, cnt[ch]);
		x -= num, cnt[ch] -= num;
	}

	if (cnt[yuki[i]] < x) return 0;
	cnt[yuki[i]] -= x;
	return check(i + 1, x, cnt);
}

int main(){
	cin.tie(0);
	ios::sync_with_stdio(false);
	cout.setf(ios::fixed);
	cout.precision(20);

	int n;
	string s;
	cin >> n >> s;

	vector<int> cnt(256);
	rep(i, n) ++cnt[s[i]];

	int lb = 0, ub = 1e6;
	while (ub - lb > 1){
		int mid = (ub + lb) / 2;
		if (check(0, mid, cnt)) lb = mid;
		else ub = mid;
	}
	cout << lb << endl;
}