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// Karol Kosinski 2025
#include <bits/stdc++.h>
#define FOR(i,a,b) for(int i=(a),_b=(b);i<_b;++i)
#define FR_(i,a,b) for(int i=(a),_b=(b);i<=_b;++i)
#define FD_(i,b,a) for(int i=(b),_a=(a);i>=_a;--i)
#define ALL(c) (c).begin(),(c).end()
#define SIZE(c) int((c).size())
#define X first
#define Y second
#define endl '\n'
#define NAM(x) #x,'=',x
using namespace std;
using LL = long long;
using ULL = unsigned long long;
using PII = pair<int, int>;
using TIII = tuple<int, int, int>;
template<class...T> void _cout(T...a){(cout<<...<<a);}

#ifndef ENABLE_DEBUG
#define DEB(k,p,f,x...)
#else
#define DEB(k,p,f,x...) {if(k)_cout("------",setw(4),__LINE__," : ",__FUNCTION__,endl);if(p)f(x);}
#endif
#define DEBF(f,x...)    DEB(1,1,f,x)
#define DEBL            DEBF(void,0)
#define DEBC(p,x...)    DEB(0,p,_cout,x)
#define DEBUG(x...)     DEBC(1,x)

constexpr int NX = 8'005;

int n, k, t;
int T[NX], A[NX], B[NX];
string s;

void count_t_inter()
{
    FOR(i,0,t) if ( s[i] != '3' ) ++ T[0];
    DEBUG( "** ", T[0], ' ' );
    FOR( i, 1, n + 1 - t )
    {
        T[i] = T[ i - 1 ];
        if ( s[ i - 1 ] != '3' ) -- T[i];
        if ( s[ i + t - 1 ] != '3' ) ++ T[i];
        DEBUG( T[i], ' ' );
    }
    DEBUG(endl);
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cin >> n >> k >> t >> s;

    int W[3] = {0,0,0};
    FOR (i,0,n) ++ W[ s[i] - '1' ];
    int res = ( k < W[0] ) ? -1 : min( n, k + W[2] );

    count_t_inter();
    FR_(i,1,n) A[i] = A[ i - 1 ] + int( s[ i - 1 ] == '3' );
    FR_(i,1,n) B[i] = B[ i - 1 ] + int( s[ i - 1 ] == '1' );

    FOR(i,0,n)
    {
        int val = i + 2 * t;
        if ( val >= n ) break;
        FOR(j,val,n)
        {
           DEBUG( "------ (", i, ", ", j, ") ------\n" );
           int x = T[i] + T[ j - t + 1 ];
           int o = B[i] + B[n] - B[ j + 1 ];
           if ( x + o > k ) continue;
           int w = A[i] + A[n] - A[ j + 1 ] + k - x;
           int r = min( w, i + n - j - 1 );
           DEBUG( "** ", NAM(x), "  ", NAM(o), "  ",NAM(r), endl );
           res = max( res, r );
        }
    }
    cout << res << endl;
    return 0;
}