#include<stdio.h>
#include<stdlib.h>

int main(void){
    double a,b,c,d;
    scanf("%lf,%lf,%lf,%lf",&a,&b,&c,&d);
    double X = a/d;
    double Y = c/b;
    if(X>=Y){
        printf("Yes");
    } else{
        printf("No");
    }
    return 0;
}