#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
const int MAXN = 200005;
const int INF = 0x3f3f3f3f;

template <typename T> inline void cmin(T &x, T y) {
    if (x > y) x = y;
}

int n, m, k;
char s[MAXN];
int sum[MAXN], dp[MAXN][6][2];

bool Check(int mid) {
    memset(dp, 0x3f, sizeof(dp));
    dp[0][0][0] = 0;
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j <= k; ++j) {
            if (dp[i][j][0] != INF) {
                cmin(dp[i + 1][j][0], dp[i][j][0]);
                if (i + mid <= n && j < k) {
                    cmin(dp[i + mid][j + 1][1], dp[i][j][0] + sum[i + mid] - sum[i]);
                }
            }
            if (dp[i][j][1] != INF) {
                cmin(dp[i + 1][j][0], dp[i][j][1] + (s[i + 1] != '0'));
                cmin(dp[i + 1][j][1], dp[i][j][1] + (s[i + 1] != '1'));
            }
        }
    }
    return min(dp[n][k][0], dp[n][k][1]) <= m;
}

void solve() {
    scanf("%d %d %d", &n, &m, &k);
    scanf("%s", s + 1);
    for (int i = 1; i <= n; ++i) {
        sum[i] = sum[i - 1] + (s[i] == '0');
    }
    int L = 1, R = n / k, ans = -1;
    while (L <= R) {
        int mid = (L + R) >> 1;
        if (Check(mid)) {
            ans = mid;
            L = mid + 1;
        } else {
            R = mid - 1;
        }
    }
    printf("%d\n", ans);
}

int main() {
    solve();
    return 0;
}