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#include <bits/stdc++.h>
#define fi first
#define sc second
#define pb push_back
#define rep(i,p,k) for(int i=(p);i<(k);++i)
#define forn(i,p,k) for(int i=(p);i<=(k);++i)
#define forr(i,k,p) for(int i=(k)-1;i>=(p);--i)
#define each(a,b) for(auto&a:b)
#define all(v)  begin(v), end(v)
#define RET(smth)   return void(cout<<(smth)<<'\n');
#define sz(v) (int)v.size()
using namespace std;
using pii = pair<int,int>;
using ll = long long;
using lll = __int128_t;
using Vi = vector<int>;
#ifdef DEBUG
#include "debug.h"
#else
#define debug(...) ;
#endif



int main() {
#ifndef DEBUG
    cin.tie(0) -> sync_with_stdio(0);
#endif
    int n,k,t; cin >> n >> k >> t;
    vector<int> p1(n+1), p2(n+1); // both, online
    string s; cin >> s;
    rep(i,0,n) {
        p1[i+1] = p1[i] + (s[i] != '3');
        p2[i+1] = p2[i] + (s[i] == '2');
    }
    k = max(0,p1[n] - k);
    int res = p2[n] >= k ? n - k : -1;
    auto sum1 = [&](int a, int b) {return a <= b ? p1[b+1]-p1[a] : 0;};
    auto sum2 = [&](int a, int b) {return a <= b ? p2[b+1]-p2[a] : 0;};
    rep(i,t,n) rep(j,i,n-t) if(sum2(0,i-t-1) + sum1(i,j) + sum2(j+t+1, n-1) >= k) res = max(res, n - (j - i + 2*t + 1) - max(0,k - sum1(i,j)));
    cout << res << '\n';
    return 0;
}