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// Witold Milewski
// PA 2025
#include <bits/stdc++.h>
using namespace std;
#define FOR(i, a, b) for(int i=a; i<=b; ++i)
#define FORB(i, b, a) for(int i=b; i>=a; --i)
#define sz(A) (int)(A.size())
#define eb emplace_back
#define pb push_back
#define pi pair<int, int>
#define f first
#define s second
#define rs resize
#define V vector

const int maxn=8007;

int P[6][maxn];
int S[5][maxn];

int n, k, t, w, odp=-1;
V<int> A;

signed main() {
  cin.tie(0) -> ios_base::sync_with_stdio(0);
  cin >> n >> k >> t;
  A.rs(n+1);
  string inp; cin >> inp;
  FOR(i, 1, n) A[i]=inp[i-1]-'1'+1;
  FOR(z, 1, 3) FOR(i, 1, n) P[z][i]=P[z][i-1]+(A[i]==z);
  FOR(z, 1, 3) FORB(i, n, 1) S[z][i]=S[z][i+1]+(A[i]==z);
  FOR(i, 1, n) {
    P[4][i]=P[1][i]+P[3][i];
    S[4][i]=S[1][i]+S[3][i];
    P[5][i]=P[1][i]+P[2][i];
  }
  k=min(k, P[1][n]+P[2][n]);
  w=P[1][n]+P[2][n]-k;
  
  if(P[2][n]>=w) odp=max(odp, P[3][n]+P[1][n]+P[2][n]-w);

  FOR(a, t+1, n-t) {
    int p = a-t-1;
    FOR(b, a, n-t) {
      int s = b+t+1;
      int x = P[5][b] - P[5][a-1];
      int y = P[2][p] + S[2][s];
      int cos = x+y;
      if(cos>=w) {
        int z = min(cos-w, y);
        odp=max(odp, P[4][p] + S[4][s] + z);
      }
    }
  }

  cout << odp << '\n';
}