#include <bits/stdc++.h>
#define F first
#define S second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define int long long
using namespace std;
#ifdef LOCAL
#define WOSAOJI freopen("in.txt", "r", stdin);
#else
#define WOSAOJI ios_base::sync_with_stdio(0), cin.tie(0);
#endif
#define chmax(a, b) (a) = (a) > (b) ? (a) : (b)
#define chmin(a, b) (a) = (a) < (b) ? (a) : (b)
int n, k;
string s;
int calc(int i, vector<vector<int>> &cnt) {
int here = i;
i--;
i = lower_bound(all(cnt[0]), cnt[0][i] + k) - cnt[0].begin();
if (i > n) return 1 << 30;
i = lower_bound(all(cnt[1]), cnt[1][i] + k) - cnt[1].begin();
if (i > n) return 1 << 30;
i = lower_bound(all(cnt[2]), cnt[2][i] + k) - cnt[2].begin();
if (i > n) return 1 << 30;
return i - here + 1;
}
signed main() {
WOSAOJI
cin >> n >> k;
cin >> s;
vector<vector<int>> cnt(3, vector<int>(n + 1, 0));
s = " " + s;
for (int i = 1; i <= n; i++) {
for (int j = 0; j < 3; j++) cnt[j][i] = cnt[j][i - 1];
if (s[i] == 'J') cnt[0][i]++;
if (s[i] == 'O') cnt[1][i]++;
if (s[i] == 'I') cnt[2][i]++;
}
int ans = 1 << 30;
for (int i = 1; i <= n; i++) {
if (s[i] == 'J') chmin(ans, calc(i, cnt));
}
if (ans == 1 << 30) ans = k * 3 - 1;
cout << ans - k * 3 << '\n';
}
