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#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define rep(a, b) for(int a = 0; a < (b); ++a)
#define st first
#define nd second
#define pb push_back
#define all(a) a.begin(), a.end()
const int LIM=8e3+7;
int pref[3][LIM];
int licz(int a, int b, int c, int k) {
	if(a>k) return -1;
	if(a+b<=k) return a+b+c;
	return c+k;
}
int sum(int t, int l, int r) {
	if(l>r) return 0;
	return pref[t][r+1]-pref[t][l];
}
int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
	int n, k, t;
	string s;
	cin >> n >> k >> t >> s;
	rep(i, n) {
		rep(j, 3) pref[j][i+1]=pref[j][i];
		++pref[s[i]-'1'][i+1];
	}
	int ans=licz(pref[0][n], pref[1][n], pref[2][n], k);
	rep(i, n) for(int j=i+2*t-1; j<n; ++j) {
		int nk=k-sum(0, i, i+t-1)-sum(1, i, i+t-1)-sum(0, j-t+1, j)-sum(1, j-t+1, j);
		ans=max(ans, licz(sum(0, 0, i-1)+sum(0, j+1, n-1), sum(1, 0, i-1)+sum(1, j+1, n-1), sum(2, 0, i-1)+sum(2, j+1, n-1), nk));
	}
	cout << ans << '\n';
}