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#include <bits/stdc++.h>
using namespace std;

#define mp make_pair
#define pb push_back
#define st first
#define nd second
#define fi first
#define se second
#define vt vector
#define FOR(a, b, c)  for(int a=b; a<c; ++a)
#define all(a)     (a).begin(),(a).end()
#define sz(a)      (int)(a).size()

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> pll;
typedef pair<int, int> pii;
typedef vector<int> vi; 
typedef vector<ll> vll;
typedef pii PII;
typedef pll PLL;

constexpr ll nax = 2e5+6969, INF = 1e9+2137;
constexpr ld eps = 1e-9;

mt19937_64 rng(6969);
// mt19937_64 rng(chrono::system_clock::now().time_since_epoch().count());

inline ll rand(ll l, ll r) {
	return uniform_int_distribution<ll>(l, r)(rng);
}

int n, k, t, ans; 
int pref[4][nax];

int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);

    cin >> n >> k >> t; 
    string s; 
    cin >> s; 

    for(int i = 0; i < n; i++) {
        pref[s[i] - '0'][i+1]++; 
    }
    for(int i = 1; i <= n; i++) {
        pref[1][i] += pref[1][i-1]; 
        pref[2][i] += pref[2][i-1]; 
        pref[3][i] += pref[3][i-1]; 
    }

    ans = -1; 

    if(pref[1][n] <= k) {
        ans = n - pref[2][n] + min(k - pref[1][n], pref[2][n]); 
    }


    for(int i = 1; i <= n; i++) {
        for(int j = i+t; j <= n - t + 1; j++) {
            int skipped = pref[1][i+t-1] + pref[1][n] - pref[1][j-1];
            skipped += pref[2][i+t-1] - pref[2][i-1] + pref[2][j + t - 1] - pref[2][j-1]; 
            if(skipped > k) {
                continue; 
            }

            int twos = pref[2][i-1] + pref[2][n] - pref[2][j+t-1]; 
            
            int cur = i - 1 + (n - (j + t - 1)) - twos; 
            cur += min(k - skipped, twos); 
            ans = max(ans, cur); 
        }
    }
    cout << ans << "\n"; 
    return 0;
}