a,b = [int(n) for n in input().split(" ")]
c = [int(n) for n in input().split(" ")]
x,y = c
xx = x - 1
yy = y - 1
if xx // b % 2 == 0:
    anum = x % b
else:
    anum = ( - (x % b - 1)) % b
if yy // b % 2 == 0:
    bnum = y % b
else:
    bnum = ( - (y % b - 1)) % b
if anum == bnum:
    print("YES")
else:
    print("NO")