#------------------------------------------------------------------------------
#  Loop5.py
#  Computes the nth Triangular number: 0+1+2+3+....+n
#------------------------------------------------------------------------------

#get n from user
n = int(input("Enter a non-negative integer: "))
sum = 0
for k in range(n+1):  #  same as range(0, n+1)
   sum += k
   #print(sum)
#end for
print(sum)