#include <bits/stdc++.h>
using namespace std;
const int N=2e5+10,inf=1e9+10;
int n,m,k,a[N],f[N][6],g[N][6];
char c[N];
void read(){
    cin>>n>>m>>k;
    for(int i=1;i<=n;i++){
        cin>>c[i];
        a[i]=c[i]-'0';
        a[i]+=a[i-1];
    }
}
int val(int l,int r){
    return (r-l+1)-(a[r]-a[l-1]);
}
bool check(int x){
    for(int i=0;i<=n;i++) for(int j=0;j<=5;j++) f[i][j]=g[i][j]=inf;
    for(int i=0;i<=n;i++) f[i][0]=g[i][0]=0;
    for(int j=1;j<=k;j++){
        if(j==1) f[x][j]=val(1,x);
        for(int i=x+1;i<=n;i++){
            f[i][j]=g[i-x-1][j-1]+val(i-x+1,i);
            if(i!=n && c[i+1]=='0') g[i][j]=min(f[i][j],g[i-1][j]);
            else g[i][j]=g[i-1][j];
        }
    }
    return (f[n][k]<=m);
}
void work(){
    int L=1,R=n+1;
    while(L<R){
        int mid=(L+R)>>1;
        if(check(mid)) L=mid+1;
        else R=mid;
    }
    if(L==1) cout<<"-1\n";
    else cout<<L-1<<'\n';
}
int main(){
    ios::sync_with_stdio(false);
    std::cin.tie(0);
    std::cout.tie(0);
    // freopen("nzq.in","r",stdin);
    // freopen("nzq.out","w",stdout);
    read();
    work();
    cerr<<1.0*clock()/CLOCKS_PER_SEC<<'\n';
    return 0;
}