# n = int(input("Number pleases, "))
# sum = n(n+1)/2
# print(sum)

# n = int(input("Number pleases, "))
# sum = sum(i for i in range(n+1))
# print(sum)

# n = int(input("Number pleases, "))
# s = 0    #khai bao diem bat dau
# for i in range(1, n+1):
#     s += i**2   #tinh tong voi tung i roi xuong
#     # print(i)
#     # print(s)
# print(s)

n = int(input("Number pleases, "))
r = range(1, n + 1)
sum = sum(r)
print(sum)