#include <string>
#include <vector>
#include <algorithm>
#include <numeric>
#include <set>
#include <map>
#include <queue>
#include <iostream>
#include <sstream>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <cstring>
#include <cctype>
#include <cassert>
#include <limits>
#include <functional>
#define rep(i,n) for(int (i)=0;(i)<(int)(n);++(i))
#define rer(i,l,u) for(int (i)=(int)(l);(i)<=(int)(u);++(i))
#define reu(i,l,u) for(int (i)=(int)(l);(i)<(int)(u);++(i))
#if defined(_MSC_VER) || __cplusplus > 199711L
#define aut(r,v) auto r = (v)
#else
#define aut(r,v) __typeof(v) r = (v)
#endif
#define each(it,o) for(aut(it, (o).begin()); it != (o).end(); ++ it)
#define all(o) (o).begin(), (o).end()
#define pb(x) push_back(x)
#define mp(x,y) make_pair((x),(y))
#define mset(m,v) memset(m,v,sizeof(m))
#define INF 0x3f3f3f3f
#define INFL 0x3f3f3f3f3f3f3f3fLL
using namespace std;
typedef vector<int> vi; typedef pair<int,int> pii; typedef vector<pair<int,int> > vpii; typedef long long ll;
template<typename T, typename U> inline void amin(T &x, U y) { if(y < x) x = y; }
template<typename T, typename U> inline void amax(T &x, U y) { if(x < y) x = y; }

int main() {
	int N;
	while(~scanf("%d", &N)) {
		char *S = new char[N + 1];
		scanf("%s", S);
		int cnt[26] = {};
		rep(i, N) {
			char c = S[i];
			++ cnt[c - 'a'];
		}
		vi curs(26);
		rep(i, 26)
			curs[i] = cnt[25 - i];
		vector<vi> trans;
		rer(a, 'y' + 1, 'z')
			trans.push_back({a});
		rer(a, 'u' + 1, 'z')
			trans.push_back({'y', a});
		rer(a, 'k' + 1, 'z')
			trans.push_back({'y', 'u', a});
		rer(a, 'i' + 1, 'z')
			trans.push_back({'y', 'u', 'k', a});
		rer(a, 'a', 'z')
			trans.push_back({'y', 'u', 'k', 'i', a});
		each(i, trans) {
			each(j, *i)
				*j = 25 - (*j - 'a');
		}
		int ans = 0;
		while(1) {
			vi maxs;
			each(i, trans) {
				bool ok = true;
				each(j, *i)
					ok &= -- curs[*j] >= 0;
				if(ok)
					amax(maxs, curs);
				each(j, *i)
					++ curs[*j];
			}
			if(maxs.empty())
				break;
			curs = maxs;
			++ ans;
		}
		printf("%d\n", ans);
	}
	return 0;
}