from math import *

blad_oczekiwany = 0.0000005
n = 0
    
def blad_wzgledny(x0, x):
    return fabs(x - x0) / x

def wyznacz_e(n):
    e = 0.0
    next = 1.0
    for i in range(n):
        if i != 0:
            next *= 1.0/i
        e += next
    return e

while blad_wzgledny(wyznacz_e(n), e) > blad_oczekiwany:
    n += 1

print(n)