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

const ll BIG = 1e6 + 9 ;
ll tc , x , y , a , b ;

int main()
{
    ll a , b , c , d ;
    bool win = 1;
    cin >> a >> b >> c >> d ;
    bool sw = 0 ;
    while ( a > 0 && c > 0 )
    {
        sw ? a -= d : c -= b ;
        sw = !sw ;
    }
    if ( a <= 0 )
        win = 0 ;
    cout << ( win ? "Yes" : "No" ) ;

}


Measured memory_bytes: 3620