There are N children in AtCoder Kindergarten. Mr. Evi will arrange the children in a line, then give 1 candy to the first child in the line, 2 candies to the second child, ..., N candies to the N-th child. How many candies will be necessary in total?
N=int(input())
print(N*(N+1)/2)











N=int(input())

sum_candy=(N * (N+1) / 2)
print(int(sum_candy))


