#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  const map<char, int> m{{'c', 0}, {'o', 1}, {'n', 2}};
  int n; string s; cin >> n >> s;
  int num[3][3]{};
  REP(i, n * 3) {
    const auto it = m.find(s[i]);
    if (it != m.end()) ++num[i % 3][it->second];
  }
  int ans = min({num[0][0], num[1][1], num[2][2]}), cap = n - ans;
  const int tmp1 = min({num[1][0], num[2][1], num[0][2], cap - 1});
  ans += tmp1;
  cap -= tmp1;
  const int tmp2 = min({num[2][0], num[0][1], num[1][2], cap - 1});
  ans += tmp2;
  cap -= tmp2;
  cout << ans << '\n';
  return 0;
}