#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef pair<ll,ll> P;
typedef vector<ll> VI;
typedef vector<VI> VVI;
#define REP(i,n) for(int i=0;i<n;i++)
#define ALL(v) v.begin(),v.end()
constexpr ll MOD=998244353;
constexpr ll INF=1e18;

int main(){
    int n, k; cin >> n >> k; n--;
    string s; cin >> s;
    reverse(ALL(s));
    REP(i,n){
        if(s[i]=='o'){
            if(n-i<=k){
                cout << n-i << endl;
                return 0;
            }
            i+=k;
        }
    }
    cout << 0 << endl;
    return 0;
}