#include <bits/stdc++.h>

using namespace std;
#define ll long long
#define pll pair<ll, ll>
#define INF 0x3f3f3f3f3f3f3f3f

const int N = 2e5 + 10;
ll n, m, k;
string s;

ll dp[N][6][2];
ll sum[N];


bool check(ll x){
    for (int i = 0; i <= n; i ++){
        for (int j = 0; j <= k; j ++){
            dp[i][j][0] = dp[i][j][1] = INF;
        }
    }

    dp[0][0][0] = 0;
    for (int i = 1; i <= n; i ++){
        for (int j = 0; j <= k; j ++){
            if (s[i] == '0'){
                dp[i][j][0] = min(dp[i][j][0], min(dp[i - 1][j][0], dp[i - 1][j][1]));
                dp[i][j][1] = min(dp[i][j][1], dp[i - 1][j][1] + 1);
            }else if (s[i] == '1'){
                dp[i][j][0] = min(dp[i][j][0], dp[i - 1][j][0]);
                dp[i][j][1] = min(dp[i][j][1], dp[i - 1][j][1]);
            }
            if (i >= x && j >= 1) 
                dp[i][j][1] = min(dp[i][j][1], dp[i - x][j - 1][0] + sum[i] - sum[i - x]);
        }
    }


/*
    if s[i] == '0' dp[i][k][0] = min dp[i - 1][k][0] dp[i - 1][k][1]
                   dp[i][k][1] = min dp[i - 1][j][1] + 1
    if s[i] == '1' dp[i][k][0] = min dp[i - 1][k][0]
                   dp[i][k][1] = min dp[i - 1][k][1]
*/
    ll minn = min(dp[n][k][1], dp[n][k][0]);
    return minn <= k;

}


void solve(){
    cin >> n >> m >> k;
    cin >> s; s = " " + s;
    
    for (int i = 1; i <= n; i ++){
        sum[i] = sum[i - 1] + (s[i] == '0' ? 1 : 0);
    }

    ll l = 0, r = n + 3;
    while (l + 1 < r){
        ll mid = (l + r) >> 1;
        if (check(mid)) l = mid;
        else r = mid;
    }

    ll ans = (l == 0 ? -1 : l);
    cout << ans << endl;

}

int main(){
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t = 1;
    // cin >> t;
    while (t --) solve();
}

/*
8 2 1
10010101
*/