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#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;

const int N = 8e3+100;

int n, k, x, prf[N][4];
int sp[N];

void solve() {
    cin>>n>>k>>x;
    string s; cin>>s;

    for (int i=1; i<=n; ++i) {
        sp[i] = s[i-1] - '0';
        for (int j=0; j<4; ++j) {
            prf[i][j] = prf[i-1][j] + (sp[i] == j);
        }
    }

    // jedzie do biura co najmniej raz
    int ans = -1;
    for (int l=1; l<=n; ++l) {
        for (int r=l; r<=n; ++r) {
            if (l-x < 1 || r+x > n) continue;
            int cp = k - (prf[l-1][1] + (prf[n][1] - prf[r][1]));
            cp -= (prf[l-1][2] - prf[l-x-1][2]) + (prf[r+x][2] - prf[r][2]);
            if (cp < 0) continue;
            int lf3 = prf[l-x-1][3] + (prf[n][3] - prf[r+x][3]);
            int lf2 = min(cp, prf[l-x-1][2] + (prf[n][2] - prf[r+x][2]));
            int lf1 = prf[l-x-1][1] + (prf[n][1] - prf[r+x][1]);
            ans = max(ans, lf3 + lf2 + lf1);
        }
    }

    // caly dzien w domu
    int s1 = prf[n][1];
    int cp = k - s1;
    if (cp >= 0) {
        ans = max(ans, prf[n][3] + min(cp, prf[n][2]) + prf[n][1]);
    }

    cout<<ans<<"\n";
}

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