#include<bits/stdc++.h>
using namespace std;
const int N = 8002;

int n,pref1[N],pref2[N],pref3[N],k,t;
string s;
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> k >> t >> s;
    for(int i = 1;i <= n;i++){
        pref1[i] = pref1[i-1] + (s[i-1] == '1');
        pref2[i] = pref2[i-1] + (s[i-1] == '2');
        pref3[i] = pref3[i-1] + (s[i-1] == '3');
    }
    int max_res = -1;
    if(pref1[n] <= k){
        max_res = max(max_res,pref3[n] + pref1[n] + min(k - pref1[n],pref2[n]));
    }
    for(int i = t+1;i <= n-t;i++){
        for(int j = i;j <= n-t;j++){
            int pominiete = pref1[n] - pref1[j] + pref1[i-1] + pref2[i-1] - pref2[i-t-1] + pref2[j+t] - pref2[j];
            if(pominiete > k)continue;
            max_res = max(max_res,pref3[n] - pref3[j+t] + pref3[i-t-1] + pref1[n] - pref1[j+t] + pref1[i-t-1] + min(k - pominiete,pref1[j] - pref1[i-1] + pref2[n] - pref2[j+t] + pref2[j] - pref2[i-1] + pref2[i-t-1]));
        }
    }
    cout << max_res << "\n";
    //cout << pref1[n] << " " << pref2[n] << " " << pref3[n];
}