// github.com/Johniel/contests
// yukicoder/2073/main.cpp

#include <bits/stdc++.h>

#define each(i, c) for (auto& i : c)
#define unless(cond) if (!(cond))
// #define endl "\n"

using namespace std;

template<typename P, typename Q> ostream& operator << (ostream& os, pair<P, Q> p) { os << "(" << p.first << "," << p.second << ")"; return os; }
template<typename P, typename Q> istream& operator >> (istream& is, pair<P, Q>& p) { is >> p.first >> p.second; return is; }
template<typename T> ostream& operator << (ostream& os, vector<T> v) { os << "("; for (auto& i: v) os << i << ","; os << ")"; return os; }
template<typename T> istream& operator >> (istream& is, vector<T>& v) { for (auto& i: v) is >> i; return is; }
template<typename T> ostream& operator << (ostream& os, set<T> s) { os << "#{"; for (auto& i: s) os << i << ","; os << "}"; return os; }
template<typename K, typename V> ostream& operator << (ostream& os, map<K, V> m) { os << "{"; for (auto& i: m) os << i << ","; os << "}"; return os; }
template<typename E, size_t N> istream& operator >> (istream& is, array<E, N>& a) { for (auto& i: a) is >> i; return is; }
template<typename E, size_t N> ostream& operator << (ostream& os, array<E, N>& a) { os << "[]{"; for (auto& i: a) os << i << ","; os << "}"; return os; }

template<typename T> inline T setmax(T& a, T b) { return a = std::max(a, b); }
template<typename T> inline T setmin(T& a, T b) { return a = std::min(a, b); }

using lli = long long int;
using ull = unsigned long long;
using str = string;
template<typename T> using vec = vector<T>;

constexpr array<int, 8> di({0, 1, -1, 0, 1, -1, 1, -1});
constexpr array<int, 8> dj({1, 0, 0, -1, 1, -1, -1, 1});
constexpr lli mod = 1e9 + 7;
// constexpr lli mod = 998244353;

int main(int argc, char *argv[])
{
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.setf(ios_base::fixed);
  cout.precision(15);

  int n;
  str s;
  while (cin >> n >> s) {
    str a, b, c;
    for (int i = 0; i < s.size(); ++i) {
      if (i % 3 == 0) a += s[i];
      if (i % 3 == 1) b += s[i];
      if (i % 3 == 2) c += s[i];
    }
    int r = 0;
    {
      int x = count(a.begin(), a.end(), 'c');
      int y = count(b.begin(), b.end(), 'o');
      int z = count(c.begin(), c.end(), 'n');
      r += min({x, y, z});
    }
    {
      int x = count(a.begin(), a.end(), 'o');
      int y = count(b.begin(), b.end(), 'n');
      int z = count(c.begin(), c.end(), 'c');
      r += min({x, y, z});
    }
    {
      int x = count(a.begin(), a.end(), 'n');
      int y = count(b.begin(), b.end(), 'c');
      int z = count(c.begin(), c.end(), 'o');
      r += min({x, y, z});
    }
    cout << r << endl;
  }

  return 0;
}