#include <stdio.h>

int main(int argc, char const* argv[])
{
    //1<A,H<100
    int takaA,takaH;
    int aoA,aoH;
    int takaC,aoC;
    if (scanf("%d%d%d%d",&takaH,&takaA,&aoH,&aoA)!=4) {
        return -1;
    }
    takaC=aoH/takaA;
    aoC=takaH/aoA;
    if(aoH%takaA!=0) takaC++;
    if(takaH%aoA!=0) aoC++;
    if(takaC<=aoC) printf("Yes\n");
    else printf("No\n");
    return 0;
}