#include <cstdio>
#include <algorithm>

using namespace std;

const int N = 2e5 + 500;
const int INF = 0x3f3f3f3f;

int cst[N], P[N], A[N], dp[N][6], n, m, k;

int get(int l, int r) {
	return P[r] - (l ? P[l - 1] : 0);
}

bool check(int x) {
	for(int i = 0;i + x <= n;i++) {
		cst[i] = (int)(i && A[i - 1]) + x - get(i, i + x - 1);
	}
	for(int j = 1;j <= k;j++) {
		for(int i = 0;i <= n;i++) dp[i][j] = INF;
		if(j == k) {
			for(int i = 0;i + x <= n;i++)
				dp[i + x][j] = min(dp[i + x][j], dp[i][j - 1] + cst[i]);
		} else {
			for(int i = 0;i + x + 1 <= n;i++)
				dp[i + x + 1][j] = min(dp[i + x + 1][j], dp[i][j - 1] + cst[i]);
		}
	}
	for(int i = 0;i <= n;i++)
		if(dp[i][k] <= m) return 1;
	return 0;
}

int main(){
	scanf("%d%d%d", &n, &m, &k);
	for(int i = 0;i < n;i++) {
		char c; scanf(" %c", &c);
		A[i] = c - '0'; P[i] = (i ? P[i - 1] : 0) + A[i];
	}
	int ans = 0;
	for(int i = 17;i >= 0;i--)
		if(ans + (1 << i) <= n / k && check(ans + (1 << i))) ans += (1 << i);
	printf("%d\n", ans ? ans : -1);
	return 0;
}