python 代码

a = int(input())
def gcd(a,b):
    if b == 0:
        return a
    else:
        return gcd(b,a % b)

def dfs(a,d):
    if a // d == 0:
        return a % d
    ans = a // d
    cnt = a % d
    if ans >= d:
        cnt = cnt + dfs(ans,d)
    else:
        cnt = cnt + ans
    return cnt

sum = 0
for i in range(2,a):
    sum = sum + dfs(a,i)
c = gcd(a-2,sum)
mother = (a - 2) // c
son = sum // c
print(f"{son}/{mother}")