pb3

#!/usr/bin/python

import math

def Suma(n):
    sum = 0.0
    for i in range (0,n):
        sum += (i + 1) / float(math.factorial(i))
    return sum * 0.5

while True:

    try:
        err = input("err = ")
        err = float(err)
        if err < 0:
            print("Introduceti un numar pozitiv")
        else :
            n = 1
            sum = 0.0
            while True:
                sum = Suma(n)
                n += 1
                if(err >= math.e - sum):
                    print(math.e - sum)
                    break
            break
    except Exception as e:
        print(e)
        print("Introduceti un numar valid")