#include <bits/stdc++.h>
#define maxn 100
using namespace std;
int f[maxn][maxn];
int a[maxn];
int n, k;

int num(int l, int r) {
	int ans = 0;
	for (l; l <= r; l++) {
		ans += a[l];
	}
	return ans;
}

int main() {
	cin >> n >> k;
	getchar();
	for (int i = 1; i <= n; i++) {
		char ch = getchar();
		a[i] =  ch - '0';
	}
	memset(f, 0, sizeof(f));
	f[2][1] = a[1] * a[2];
	for (int i = 2; i <= n; i++) {
		for (int j = 1; j <= k && j < i; j++) {
			for (int k = j; k < i; k++) {
//				printf("i:%d j:%d k:%d f[k][j-1]:%d num:%d mult:%d f[i][j]:%d\n", i, j, k, f[k][j - 1], num(k + 1, i),
//				       f[k][j - 1] * num(k + 1, i), f[i][j]);
				f[i][j] = max(f[k][j - 1] * num(k + 1, i), f[i][j]);
			}
		}
	}
	cout << f[n][k];
	return 0;
}

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