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#include <bits/stdc++.h>

using namespace std;

#define ll long long

#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;

typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;

typedef pair<int,int> ii;

template<class t> using vc=vector<t>;
template<class t> using vvc=vc<vc<t>>;

const int MOD = 998244353;

ll read(){
    ll i;
    cin>>i;
    return i;
}

vi readvi(int n,int off=0,int shift=0){
    vi v(n+shift);
    rep(i,shift)v[i]=0;
    rep(i,n)v[i+shift]=read()+off;
    return v;
}

void YesNo(bool condition, bool do_exit=true) {
    if (condition)
        cout << "Yes" << endl;
    else
        cout << "No" << endl;
    if (do_exit)
        exit(0);
}

void print_vi (vi & a) {
    for (auto x : a)
        cout << x << " ";
    cout << "\n";
}

int main(void ) {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

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

    string s;
    cin >> s;

    vvi pref(4,vi(n,0));
    vvi suf(4,vi(n,0));

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

    suf[s[n-1]-'1'+1][n-1] = 1;
    for (int i=n-2; i>=0; --i) {
        for (int j : {1,2,3})
            suf[j][i] = suf[j][i+1];
        ++suf[s[i] - '1' + 1][i];
    }

    int num1 = pref[1][n-1];
    int num2 = pref[2][n-1];

    if (k >= num1) {
        cout << n - max(num1 + num2 - k, 0) << '\n';
        return 0;
    }

    int res = -1;
    for (int a=0; a+2*t<=n; ++a)
        for (int b=a+t; b+t<=n; ++b) {
            int forced = pref[1][a+t-1] + suf[1][b] + pref[2][a+t-1] - (a > 0 ? pref[2][a-1] : 0) + suf[2][b] - (b+t < n ? suf[2][b+t] : 0);
            if (forced <= k) {
                int local_res = a + (n - b - t) - max((a>0 ? pref[2][a-1] : 0) + (b+t<n ? suf[2][b+t] : 0) - (k-forced), 0);
                res = max(res, local_res);
                //cout << a << " " << b << " " << forced << " " << local_res << endl;
            }

        }

    cout << res << '\n';

    return 0;
}