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#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#ifdef LOCAL
#include "../debug/debug.h"
#else
#define debug(...)
#define debugArr(...)
#endif

using namespace std;
using namespace __gnu_pbds;

using ll = long long;
using db = long double;
using pi = pair<int,int>;
using pl = pair<ll,ll>;
using vi = vector<int>;
using vl = vector<ll>;
using vb = vector<bool>;
using vpi = vector<pi>;
using vpl = vector<pl>;
using vvi = vector<vi>;

#define mp make_pair
#define eb emplace_back
#define pb push_back
#define x first
#define y second
#define sz(x) int((x).size())
#define bg(x) begin(x)
#define all(x) (x).begin(),(x).end()
#define rall(x) (x).rbegin(), (x).rend() 
#define rep(i,a,b) for(int i=(a);i<(b);i++)
#define per(i,a,b) for(int i=(b)-1;i>=(a);i--)
#define ft front()
#define bk back()
#define rsz resize
#define ins insert
#define each(a,x) for(auto&a:x)

template<class T> bool ckmin(T& a, T b) { return b<a?a=b,1:0; }
template<class T> bool ckmax(T& a, T b) { return b>a?a=b,1:0; }
template<class T> int lwb(vector<T>& a, const T& b) { return int(lower_bound(all(a),b)-bg(a)); }
template<class T> int upb(vector<T>& a, const T& b) { return int(upper_bound(all(a),b)-bg(a)); }
template<class T> void remdup(vector<T>& v) { sort(all(v)); v.erase(unique(all(v)),end(v)); }

constexpr int pct(int x) { return __builtin_popcount(x); }
constexpr int bitlog(int x) { return x == 0 ? 0 : 31 - __builtin_clz(x); }
constexpr int pct(ll x) { return __builtin_popcountll(x); }
constexpr int bitlog(ll x) { return x == 0 ? 0 : 63 - __builtin_clzll(x); }

constexpr ll cdiv(ll a, ll b) { return a / b + ((a ^ b) > 0 && a % b); }  // divide a by b rounded up
constexpr ll fdiv(ll a, ll b) { return a / b - ((a ^ b) < 0 && a % b); }  // divide a by b rounded down
constexpr int cdiv(int a, int b) { return a / b + ((a ^ b) > 0 && a % b); }  // divide a by b rounded down
constexpr int fdiv(int a, int b) { return a / b - ((a ^ b) < 0 && a % b); }  // divide a by b rounded down

const pi MOVES[] = {{-1, 0}, {0, -1}, {1, 0}, {0, 1}};

#ifdef LOCAL
mt19937_64 rng(0xabadbeef);
#else
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
#endif

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

const int N = 8008;
int dp[N][N][3];
int pref[N];
const int INF = 1e9;

int sum(int l, int r) {
    return pref[r] - pref[l-1];
}

signed main() { 
    ios_base::sync_with_stdio(false); cin.tie(nullptr);

    int n, k, t;
    cin >> n >> k >> t;

    string s;
    cin >> s;

    rep(j,0,k+1) {
        rep(typ,0,3) {
            dp[0][j][typ] = -INF;
        }
    }

    dp[0][0][0] = 0;

    rep(i,0,n) {
        pref[i+1] = pref[i] + (s[i] != '3');
    }

    rep(i,1,n+1) {
        char c = s[i-1];
        rep(j,0,k+1) {
            rep(typ,0,3) {
                dp[i][j][typ] = -INF;
            }
        }

        if (i >= t) {
            int missed = sum(i - t + 1, i);
            rep(j,missed,k+1) {
                ckmax(dp[i][j][1], dp[i-t][j-missed][0]);
                ckmax(dp[i][j][2], dp[i-t][j-missed][1]);
            }
        }

        if (c == '1') {         // w biurze
            rep(j,0,k+1) {
                ckmax(dp[i][j][1], dp[i-1][j][1]);              // stacjo
            
                if (j > 0) {
                    ckmax(dp[i][j][0], dp[i-1][j-1][0] + 1);    // skip stacjo, potyczki
                    // w biurze nie robimy potyczek
                    ckmax(dp[i][j][2], dp[i-1][j-1][2] + 1);    // skip stacjo, potyczki
                }
            }
        }
        else if (c == '2') {    // zdalnie
            rep(j,0,k+1) {
                ckmax(dp[i][j][0], dp[i-1][j][0]);              // zdalne
                ckmax(dp[i][j][1], dp[i-1][j][1]);              // stacjo
                ckmax(dp[i][j][2], dp[i-1][j][2]);              // zdalne

                if (j > 0) {
                    ckmax(dp[i][j][0], dp[i-1][j-1][0] + 1);    // skip zdalnego, potyczki
                    // w biurze nie robimy potyczek
                    ckmax(dp[i][j][2], dp[i-1][j-1][2] + 1);    // skip zdalnego, potyczki
                }
            }
        }
        else {                  // wolne
            rep(j,0,k+1) {
                ckmax(dp[i][j][0], dp[i-1][j][0] + 1);  // potyczki
                ckmax(dp[i][j][1], dp[i-1][j][1]);      // stacjo
                ckmax(dp[i][j][2], dp[i-1][j][2] + 1);  // potyczki
            }
        }
    }

    int res = -INF;
    rep(i,0,k+1) {
        ckmax(res, dp[n][i][0]);
        ckmax(res, dp[n][i][2]);
    }

    ckmax(res, -1);
    cout << res << '\n';

    return 0;
}