K = int(input())
memo = {}
def f(x):
    if x>=K:return 0
    if x in memo:
        return memo[x]
    memo[x] = (f(x+1)+f(x+2)+f(x+3)+f(x+4)+f(x+5)+f(x+6))/6+1
    return memo[x]
print(f(0))