#include <bits/stdc++.h>
using namespace std;

#define _p(...) (void)printf(__VA_ARGS__)
#define forr(x,arr) for(auto&& x:arr)
#define _overload3(_1,_2,_3,name,...) name
#define _rep2(i,n) _rep3(i,0,n)
#define _rep3(i,a,b) for(int i=int(a);i<int(b);++i)
#define rep(...) _overload3(__VA_ARGS__,_rep3,_rep2,)(__VA_ARGS__)
#define _rrep2(i,n) _rrep3(i,0,n)
#define _rrep3(i,a,b) for(int i=int(b)-1;i>=int(a);i--)
#define rrep(...) _overload3(__VA_ARGS__,_rrep3,_rrep2,)(__VA_ARGS__)
#define ALL(x) (x).begin(), (x).end()
#define BIT(n) (1LL<<(n))
#define SZ(x) ((int)(x).size())
#define fst first
#define snd second
typedef long long ll;
typedef vector<int> vi;typedef vector<vi> vvi;typedef pair<int,int> pii;typedef vector<pii> vpii;

void Main() {
  int N;
  string S;
  cin >> N >> S;
  map<char, int> co;
  forr(c, S) co[c]++;

  int ans = 0;

  while (1) {
    //forr(p, co) _p("(%c,%d) ", p.fst, p.snd); _p("\n");
    bool added = 0;
    if (co['y'] && co['u'] && co['k'] && co['j']) {
      int n = min(co['y'], min(co['u'], min(co['k'], co['j'])));
      ans+=n;
      added = 1;
      co['y']-=n;
      co['u']-=n;
      co['k']-=n;
      co['j']-=n;
    }
    if (!added && co['y'] && co['u'] && co['k'] >= 2) {
      ans++;
      added = 1;
      co['y']--;
      co['u']--;
      co['k']-=2;
    }
    if (!added && co['y'] && co['u']) {
      for (char c = 'l'; c < 'u'; c++) {
        if (co[c]) {
          ans++;
          added = 1;
          co['y']--;
          co['u']--;
          co[c]--;
          break;
        }
      }
    }
    if (!added && co['y'] && co['u'] >= 2) {
      ans++;
      added = 1;
      co['y']--;
      co['u']-=2;
    }
    if (!added && co['y']) {
      for (char c = 'v'; c < 'y'; c++) {
        if (co[c]) {
          ans++;
          added = 1;
          co['y']--;
          co[c]--;
          break;
        }
      }
    }
    if (!added && co['y'] >= 2) {
      ans++;
      added = 1;
      co['y']-=2;
    }
    if (!added && co['z']) {
      ans+=co['z'];
      added = 1;
      co['z'] = 0;
    }

    if (!added) break;
  }

  _p("%d\n", ans);
}
int main() { cin.tie(0); ios::sync_with_stdio(false); Main(); return 0; }