/*/ Author: kal013 /*/
// #pragma GCC optimize ("O3")
#include "bits/stdc++.h"
#include "ext/pb_ds/assoc_container.hpp"
#include "ext/pb_ds/tree_policy.hpp"
using namespace std;
using namespace __gnu_pbds;
template<class T>
using ordered_set = tree<T, null_type,less<T>, rb_tree_tag,tree_order_statistics_node_update> ;
template<class key, class value, class cmp = std::less<key>>
using ordered_map = tree<key, value, cmp, rb_tree_tag, tree_order_statistics_node_update>;
// find_by_order(k) returns iterator to kth element starting from 0;
// order_of_key(k) returns count of elements strictly smaller than k;
struct custom_hash { // Credits: https://codeforces.com/blog/entry/62393
static uint64_t splitmix64(uint64_t x) {
// http://xorshift.di.unimi.it/splitmix64.c
x += 0x9e3779b97f4a7c15;
x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
return x ^ (x >> 31);
}
size_t operator()(uint64_t x) const {
static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
return splitmix64(x + FIXED_RANDOM);
}
};
template<class T> ostream& operator<<(ostream &os, vector<T> V) {
os << "[ ";
for(auto v : V) os << v << " ";
return os << "]";
}
template<class T> ostream& operator<<(ostream &os, set<T> S){
os << "{ ";
for(auto s:S) os<<s<<" ";
return os<<"}";
}
template<class T> ostream& operator<<(ostream &os, unordered_set<T> S){
os << "{ ";
for(auto s:S) os<<s<<" ";
return os<<"}";
}
template<class T> ostream& operator<<(ostream &os, ordered_set<T> S){
os << "{ ";
for(auto s:S) os<<s<<" ";
return os<<"}";
}
template<class L, class R> ostream& operator<<(ostream &os, pair<L,R> P) {
return os << "(" << P.first << "," << P.second << ")";
}
template<class L, class R> ostream& operator<<(ostream &os, map<L,R> M) {
os << "{ ";
for(auto m:M) os<<"("<<m.first<<":"<<m.second<<") ";
return os<<"}";
}
template<class L, class R> ostream& operator<<(ostream &os, unordered_map<L,R> M) {
os << "{ ";
for(auto m:M) os<<"("<<m.first<<":"<<m.second<<") ";
return os<<"}";
}
template<class L, class R, class chash = std::hash<R> > ostream& operator<<(ostream &os, gp_hash_table<L,R,chash> M) {
os << "{ ";
for(auto m:M) os<<"("<<m.first<<":"<<m.second<<") ";
return os<<"}";
}
#define TRACE
#ifdef TRACE
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
cerr << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
const char* comma = strchr(names + 1, ',');
cerr.write(names, comma - names) << " : " << arg1<<" | ";
__f(comma+1, args...);
}
#else
#define trace(...) 1
#endif
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
inline int64_t random_long(long long l,long long r){
uniform_int_distribution<int64_t> generator(l,r);
return generator(rng);
}
inline int64_t random_long(){
uniform_int_distribution<int64_t> generator(LLONG_MIN,LLONG_MAX);
return generator(rng);
}
/*/---------------------------Defines----------------------/*/
typedef vector<int> vi;
typedef pair<int,int> pii;
#define ll long long
#define F first
#define S second
#define pb push_back
#define endl "\n"
#define all(v) (v).begin(),(v).end()
/*/-----------------------Modular Arithmetic---------------/*/
const int mod=1e9+7;
inline int add(int x,int y){
x+=y;
if (x>=mod) return x-mod;
return x;
}
inline int sub(int x,int y){
x-=y;
if (x<0) return x+mod;
return x;
}
inline int mul(int x,int y){
return (x*1ll*y)%mod;
}
inline int power(int x,int y){
int ans=1;
while(y){
if (y&1) ans=mul(ans,x);
x=mul(x,x);
y>>=1;
}
return ans;
}
inline int inv(int x){
return power(x,mod-2);
}
/*/-----------------------------Code begins----------------------------------/*/
void solve(){
int n,k;
cin>>n>>k;
string s;
cin>>s;
vector<int> j,o,i;
for(int x = 0; x< n; ++x){
if (s[x] =='J') j.push_back(x);
else if (s[x] == 'O') o.push_back(x);
else i.push_back(x);
}
int iter_o = 0, iter_i = 0;
if (j.size() < k || o.size() < k || i.size() < k){
cout<<-1<<endl;
return;
}
int ans = n+1;
for(int z = k - 1; z < j.size(); ++z){
int l = j[z - k + 1];
while(iter_o < o.size() && o[iter_o] <= j[z]) ++iter_o;
if (iter_o + k >= o.size() + 1) break;
while(iter_i < i.size() && i[iter_i] <= o[iter_o + k -1]) ++iter_i;
if (iter_i + k >= i.size() + 1) break;
ans = min(ans, i[iter_i + k - 1] - l + 1 - 3*k );
}
if (ans > n - 3*k){
cout<<-1<<endl;
}
else{
cout<<ans<<endl;
}
}
int main(){
// Use "set_name".max_load_factor(0.25);"set_name".reserve(512); with unordered set
// Or use gp_hash_table<X,null_type>
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
cout<<fixed<<setprecision(25);
cerr<<fixed<<setprecision(10);
auto start = std::chrono::high_resolution_clock::now();
int t=1;
// cin>>t;
while(t--) {
solve();
}
auto stop = std::chrono::high_resolution_clock::now();
auto duration = std::chrono::duration_cast<std::chrono::nanoseconds>(stop - start);
// cerr << "Time taken : " << ((long double)duration.count())/((long double) 1e9) <<"s "<< endl;
}
