## Allowed 2 days Absent, but 3 or more not allowed
## https://www.hackerearth.com/problem/algorithm/graduating-5b72b1c7-bc102a51/
​
daysnum = input()
​
def attendance(days,prev1=-1,prev2=-1,missgraduation=False):

    ## Breaking Condition
    if days == 1:
        return 1

    ## DP Memoization
    if (days,prev1,prev2)  in memo:
        return memo[(days,prev1,prev2)]
​
    total = 0
​
    if prev1 == 1 and prev2 == 1:
        currval = attendance(days-1, 1,1) + attendance(days-1, 1,0)
        total += currval
        memo[(days,prev1,prev2)] = total
    elif prev1 == 0 and prev2 == 0:
        currval = attendance(days-1, 0,1)
        total += currval
        memo[(days,prev1,prev2)] = total
    elif prev1 == 1 and prev2 == 0:
        currval = attendance(days-1, 0,1) + attendance(days-1, 0,0)
        total += currval
        memo[(days,prev1,prev2)] = total
    elif prev1 == 0 and prev2 == 1:
        currval = attendance(days-1, 1,1) + attendance(days-1, 1,0)
        total += currval
        memo[(days,prev1,prev2)] = total
    else:
        if missgraduation is False:
            total += attendance(days-1, 0,1) + attendance(days-1, 0,0) + attendance(days-1, 1,0) + attendance(days-1, 1,1)
        else:
            total += attendance(days-1, 0,1) + attendance(days-1, 0,0)
​
        memo[(days,prev1,prev2)] = total

    return total
​
memo = dict()
absent = attendance(daysnum,missgraduation=True) if daysnum > 1 else 1
memo = dict()
result = attendance(daysnum) if daysnum > 1 else 2
memo = None
​
print(f'{absent}/{result}')