#include <stdio.h>

int main() {
    int A, B, C, D;
    
    scanf("%d %d %d %d", &A, &B, &C, &D);

    int ansA, ansC;
    ansA = A / D;
    ansC = C / B;

    if(ansA < ansC) {
        printf("Yes");    
    } else if(ansA >= ansC) {
        printf("No");
    }

    return 0;
}