#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
constexpr int INF = 1001001001;
constexpr int mod = 1000000007;
// constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int N;
    string S;
    cin >> N >> S;
    vector<int> cnt(26);
    for(int i = 0; i < N; ++i){
        cnt[S[i] - 'a'] += 1;
    }
    int ans = cnt[25];
    int prev_cnt = cnt[24];
    string t = "yuki";
    int remain = 0;
    for(int i = 1; i < 4; ++i){
        for(char c = t[i - 1] - 1; c > t[i]; --c){
            int y = min(prev_cnt, cnt[c - 'a']);
            ans += y;
            prev_cnt -= y;
            cnt[c - 'a'] -= y;
        }
        if(prev_cnt > cnt[t[i] - 'a']){
            prev_cnt = cnt[t[i] - 'a'];
        }
        else{
            int y = min(prev_cnt, cnt[t[i] - 'a'] - prev_cnt);
            ans += y;
            prev_cnt -= y;
        }
    }
    for(char c = 'i' - 1; c >= 'a'; --c){
        remain += cnt[c - 'a'];
    }
    ans += min(prev_cnt, remain);
    cout << ans << endl;

    return 0;
}