#include<bits/stdc++.h>
using namespace std;
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
typedef long long LL;

inline int read(){
	int x = 0 , f = 1 ; char c = getchar() ;
    while( c < '0' || c > '9' ) { if( c == '-' ) f = -1 ; c = getchar() ; } 
    while( c >= '0' && c <= '9' ) { x = x * 10 + c - '0' ; c = getchar() ; } 
    return x * f ;
}

const int maxn = 2e5+20;
int n,m,k;
int s[maxn];
char S[maxn];
int f[maxn][6][2];

bool judge(int l){
    memset(f,0x3f,sizeof(f));
    f[0][0][0] = 0;
    for(int i=1;i<=n;i++){
        for(int j=0;j<=k;j++){
            if(S[i]=='1'){
                f[i][j][1] = min(f[i][j][1],f[i-1][j][0]);
                f[i][j][1] = min(f[i][j][1],f[i-1][j][1]);
            }
            else{
                f[i][j][1] = min(f[i][j][1],f[i-1][j][0]);
                f[i][j][1] = min(f[i][j][1],f[i-1][j][1]);
                f[i][j][0] = min(f[i][j][0],f[i-1][j][0]);
                f[i][j][0] = min(f[i][j][0],f[i-1][j][1]);
            }
            if(j >= 1 && i >= l){
                f[i][j][1] = min(f[i][j][1],f[i-l][j-1][0] + l - s[i] + s[i-l]);
            }
        }
    }
    return (f[n][k][0],f[n][k][1]) <= m;
}

void solve(){
    n = read();m = read();k = read();
    scanf("%s",S+1);
    for(int i=1;i<=n;i++) S[i] -= '0';
    for(int i=1;i<=n;i++) s[i] = s[i-1] + S[i];
    if(!judge(1)) puts("-1");
    else{
        int L = 1,R = n;
        while(L<R){
            int mid = ((L+R+1)>>1);
            if(judge(mid)) L = mid;
            else R = mid - 1;
        }
        printf("%d\n",L);
    }
}

int main(){
	// freopen("1.txt","r",stdin);
	int T = 1;
	// T = read();
	while(T--) solve();
	return 0;
}