#include<bits/stdc++.h>
using namespace std;
const int N=200005;
int n,m,k;
char a[N];
int dp[N][6];
int chk(int mi){
	memset(dp,0x3f,sizeof(dp));
	int cost=0,tot=0;
	dp[1][0]=0;
	for(int i=1,j=0;i<=n;i++){
		while(j<=n&&(tot<mi||a[j+1]==1)) cost+=!a[++j],tot++;
		if(j>n) break;
		for(int l=0;l<k;l++) dp[i][l]=min(dp[i][l],dp[i-1][l]);
		for(int l=0;l<k;l++) dp[j+2][l+1]=min(dp[j+2][l+1],dp[i][l]+cost);
		cost-=!a[i];tot--;
	}
	int ans=0x3f3f3f3f;
	for(int i=1;i<=n+2;i++) ans=min(ans,dp[i][k]);
	return ans<=m;
}
int main(){
	cin>>n>>m>>k;
	scanf("%s",a+1);
	for(int i=1;i<=n;i++) a[i]-='0';
	int l=1,r=n;
	while(l<r){
		int mid=(l+r+1)/2;
		if(chk(mid)) l=mid;
		else r=mid-1;
	}
	if(!chk(l)) cout<<-1<<endl;
	else cout<<l;
	return 0;
}