__author__ = 'spb'
import sys
sys.stdin = open('hall.in')
sys.stdout = open('hall.out', 'w')

a, b, c, d = map(int, input().split())
res = 0
for p in range(c, d + 1):
    if p % 2 == 1:
        continue
    else:
        q = p // 2
    i = q // 2
    j = q - i
    if i * j < a:
        continue
    else:
        while i * j > b and i > 0:
            i -= 1
            j += 1
        while i * j >= a and i > 0:
            i -= 1
            j += 1
            res += 1

print(res)