#include<bits/stdc++.h>
#define int long long
typedef long long  LL;
using namespace std;
const int N = 2e5+5;
int n, m, k;
int a[N],dp[N][6][2], pre[N];
int check(int x) {
    for (int i = 0; i <= n+1; i++)
        for (int j = 1; j <= 5; j++)
            dp[i][j][0]= dp[i][j][1] = 1e18;
    for (int i = 1; i <= n+1; i++) {
        for (int j = 1; j <= 5; j++) {
            if (a[i] == 0 && i - 1 - x >= 0) {
                dp[i][j][0] = min(dp[i][j][0], dp[i - 1 - x][j - 1][0] + x - (pre[i - 1] - pre[i - 1 - x]));
                dp[i][j][0] = min(dp[i][j][0], dp[i - 1][j][0]);
                dp[i][j][0] = min(dp[i][j][0], dp[i - 1][j][1]);
            }
            else if (a[i] == 1) {
                dp[i][j][1] = min(dp[i - 1][j][0], dp[i - 1][j][1]);
            }
                
        }
    }
    return min(dp[n+1][k][1], dp[n+1][k][0]);
}
signed main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> m >> k;
    char c;
    for (int i = 1; i <= n; i++)cin >> c,a[i]=c-'0',pre[i]=a[i];
    for (int i = 1; i <= n; i++)pre[i] += pre[i - 1];
    int l = 1, r = n, mid;
    while (l < r) {
        mid = l + r+1 >> 1;
        if (check(mid) <= m)l = mid;
        else r = mid - 1;
    }
    if (check(l) <= m)cout << l << '\n';
    else cout << -1 << '\n';
    return 0;
}