#!/usr/bin/python2.7
# -*+ coding: utf-8 -*-

#def suma(n):
#    i = n-1
#    m = i-1
#    while n != 0:
#        m = n + i
#        m += m
#        return(m)

#def suma(n):
#    i = 0
#    j = 0
#    if n   
#        i = i+1
#        j = j+i
#        return(j)
        
#def suma(n):
#    i = n-1
#    j = n+i
#    while i != 0:
#        j += i
#        return(j)

def suma(n):
    i = 0
    j = 0
    while i < n:
        i += 1
        j = j+i
    return(j)


    
