p=int(input())
q=int(input())
r=int(input())
s=int(input())
def gcd(a,b):
if a<b:
a,b=b,a
count=0
while a!=b:
count+=a//b
t=a%b
a=b
b=t
if b<=1:
break
if a==b:
count+=1
if b==1:
count+=a
return count
su=0
for i in range(p,q+1):
for j in range(r,s+1):
su+=gcd(i,j)
print(su)
cD1pbnQoaW5wdXQoKSkKcT1pbnQoaW5wdXQoKSkKcj1pbnQoaW5wdXQoKSkKcz1pbnQoaW5wdXQoKSkKZGVmIGdjZChhLGIpOgoJaWYgYTxiOgoJCWEsYj1iLGEKCWNvdW50PTAKCXdoaWxlIGEhPWI6CgkJY291bnQrPWEvL2IKCQl0PWElYgoJCWE9YgoJCWI9dAoJCWlmIGI8PTE6CgkJCWJyZWFrCgkJCglpZiBhPT1iOgoJCWNvdW50Kz0xCglpZiBiPT0xOgoJCWNvdW50Kz1hCglyZXR1cm4gY291bnQKCnN1PTAKZm9yIGkgaW4gcmFuZ2UocCxxKzEpOgoJZm9yIGogaW4gcmFuZ2UocixzKzEpOgoJCXN1Kz1nY2QoaSxqKQpwcmludChzdSk=