A = list(map(int, input().split()))
if len(set(A)) != 3:
    print(0)
    exit()
    
if A[1] in [max(A), min(A)]:
    print(-1)
    exit()

def ok(p):
    B = [a % p for a in A]
    return not B[1] in [max(B), min(B)]

ans = 0
for p in range(1, max(A) + 1):
    if ok(p):
        ans += 1
        
print(ans)