#include <stdio.h>

int attack(int const attack, int HP){
    HP = HP - attack;
    return HP;
}

int main(){
    int A, B, C, D;
    scanf("%d", &A);
    scanf("%d", &B);
    scanf("%d", &C);
    scanf("%d", &D);
    int turn = 0;
    for (; A > 0 && C > 0;turn++){
        if(turn%2){
            A = attack(D, A);
        }else{
            C = attack(B, C);
        }
    }
    if(A>0){
        puts("Yes");
    }else{
        puts("No");
    }
    return 0;
}