// #include <bits/stdc++.h>
#include <iostream>
#include <cmath>
#include <algorithm>
#include <map>
#include <vector>
#include <iomanip>
#include <string>
#include <queue>
#include <set>
#include <deque>
#include <numeric>
#include <stack>
#include <chrono>
using namespace std;
void fast_io(){
// freopen("", "r", stdin);
// freopen("", "w", stdout);
ios::sync_with_stdio(0);
cin.tie(); cout.tie();
cout << setprecision(9);
}
#define int long long
#define endl '\n'
#define all(v) (v).begin(), (v).end()
#define rall(v) (v).rbegin(), (v).rend()
#define fi first
#define se second
void solve() {
int n, k; cin >> n >> k;
string s; cin >> s;
s = "." + s;
int pref[n + 1] = {};
vector<int> idxj, idxo, idxi;
for (int i = 1; i <= n; i++){
if (s[i] == 'J') idxj.push_back(i);
if (s[i] == 'O') idxo.push_back(i);
if (s[i] == 'I') idxi.push_back(i);
pref[i] = pref[i - 1] + (s[i] == 'O');
}
set<pair<int, int>> S;
int m = idxi.size();
for (int i = 0; i < m; i++){
S.insert({pref[idxi[i]], i});
}
int ans = 1e18;
m = idxj.size();
for (int i = k - 1; i < m; i++){
auto it = S.lower_bound({pref[idxj[i]] + k, 0});
if (it == S.end()) continue;
auto [val, idx] = *it;
if (idx + k - 1 < (int) idxi.size()) ans = min(ans, idxi[idx + k - 1] - idxj[i - k + 1] + 1);
}
if (ans == 1e18) ans = 3 * k - 1;
cout << ans - 3 * k << endl;
return;
}
signed main() {
fast_io();
srand(chrono::steady_clock::now().time_since_epoch().count());
int tc = 1;
// cin >> tc;
while (tc--) solve();
return 0;
}
