n, a, b = map(int, input().split())
pop = 0
if (a,b) == 0 and pop == 0:
    print(1)
    pop = 1
if (a+b)*2 <= n and pop == 0:
    print(1)
    pop = 1
if n<= 1 and pop == 0:
    print(0)
    pop = 1
if a == 0 and n <3 and pop == 0:
    print(0)
    pop = 1
if pop == 0:
    exc = 1
    variations = (a+1)*(b+1)
    print(exc+(exc // 6)*(exc % 6 == 0),'/',variations,sep='')