L,R,M,K=map(int, input().split())
l,r=L*K,R*K
a=(L*K)%M
b=(R*K)%M
if (R-L)*K+1>=M:
    print('Yes')
else:
    if a>b:
        print('Yes')
    elif a==0 or b==0:
        print('Yes')
    else:
        print('No')