#include<bits/stdc++.h>
using namespace std;
#include<atcoder/all>
using namespace atcoder;
using ll = long long;
int n;
string s;

void solve(){
	vector<int> vs(5);
	vector<int> yuki(4);
	for(int i = 0;i<n;i++){
		if(s[i]>'y'){
			vs[0]++;
		}else if(s[i]=='y'){
			yuki[0]++;
		}else if(s[i]>'u'){
			vs[1]++;
		}else if(s[i]=='u'){
			yuki[1]++;
		}else if(s[i]>'k'){
			vs[2]++;
		}else if(s[i]=='k'){
			yuki[2]++;
		}else if(s[i]>'i'){
			vs[3]++;
		}else if(s[i]=='i'){
			yuki[3]++;
		}else{
			vs[4]++;
		}
	}
	int ans = vs[0];
	vs[0] -= ans;
	{
		int add = min(vs[1],yuki[0]);
		ans += add;
		yuki[0] -= add;
		vs[1] -= add;
	}
	{
		int add = min({vs[2],yuki[0],yuki[1]});
		ans += add;
		vs[2] -= add;
		yuki[0] -= add;
		yuki[1] -= add;
	}
	{
		int add = min({vs[3],yuki[0],yuki[1],yuki[2]});
		ans += add;
		vs[3] -= add;
		yuki[0] -= add;
		yuki[1] -= add;
		yuki[2] -= add;
	}
	{
		int add = min({vs[4],yuki[0],yuki[1],yuki[2],yuki[3]});
		ans += add;
		vs[4] -= add;
		yuki[0] -= add;
		yuki[1] -= add;
		yuki[2] -= add;
		yuki[3] -= add;
	}
	{
		int add = min({yuki[0],yuki[1],yuki[2],yuki[3]/2});
		ans += add;
		yuki[0] -= add;
		yuki[1] -= add;
		yuki[2] -= add;
		yuki[3] -= add*2;
	}
	{
		int add = min({yuki[0],yuki[1],yuki[2]/2});
		ans += add;
		yuki[0] -= add;
		yuki[1] -= add;
		yuki[2] -= add*2;
	}
	{
		int add = min({yuki[0],yuki[1]/2});
		ans += add;
		yuki[0] -= add;
		yuki[1] -= add*2;
	}
	{
		int add = min({yuki[0]/2});
		ans += add;
		yuki[0] -= add*2;
	}
	cout<<ans<<endl;
}

signed main(){
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	cin >> n >> s;
	solve();
}