#include <bits/stdc++.h>

#define all(x) begin(x), end(x)

using namespace std;
using i32 = int;
using i64 = long long;
using ld = long double;

template <typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b and (a = b, true);}

template <typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b and (a = b, true);}

const i64 supl = LONG_LONG_MAX / 2 - 100;
const i32 supi = INT_MAX / 2 - 100;

void main_() {
    i32 n; cin >> n;
    string s; cin >> s;
    vector info(3, map<char, i32>());
    for (i32 i = 0 ; i < 3 * n ; i++) {
        info[i % 3][s[i]]++;
    }
    // for (auto [x, y] : info[0]) cout << x << ' ' << y << endl;
    i32 ans = 0;
    ans += min({ info[0]['c'], info[1]['o'], info[2]['n'] });
    ans += min({ info[1]['c'], info[2]['o'], info[0]['n'] });
    ans += min({ info[2]['c'], info[0]['o'], info[1]['n'] });

    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    main_();

    return 0;
}