#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using vi=vector<int>;
using pi=pair<int,int>;
#define F(i,a,b) for(int i=(a);i<=(b);i++)
#define G(i,a,b) for(int i=(a);i>=(b);i--)
#define ms(a,b) memset(a,b,sizeof(a))
#define si(a) ((int)(a).size())
#define all(a) (a).begin(),(a).end()
#define fi first
#define se second
#define pb push_back

const int N=2e5+3;
int a[N],dp[N][8];

int main(){
	cin.tie(0)->ios::sync_with_stdio(0);
	int n,m,d;
	cin>>n>>m>>d;
	F(i,1,n){
		char c;
		cin>>c;
		a[i]=c-'0';
	}
	int l=1,r=n,ans=-1;
	while(l<=r){
		int mid=(l+r)>>1;
		auto chk=[&](){
			ms(dp,63);
			F(i,0,n) dp[i][0]=0;
			F(i,1,n) G(j,d,1){
				int w=0;
				G(k,i,1){
					if(!a[k]) w++;
					if(i-k+1>=mid&&!a[k-1]){
						if(k>=2) dp[i][j]=min(dp[i][j],dp[k-2][j-1]+w);
						else if(j==1) dp[i][j]=min(dp[i][j],w);
					}
				}
				dp[i][j]=min(dp[i][j],dp[i][j+1]);
			}
			F(i,1,n) if(dp[i][d]<=m) return 1;
			return 0;
		};
		if(chk()){
			ans=mid;
			l=mid+1;
		}else r=mid-1;
	}
	cout<<ans;
}