""" a = input() for i in range(len(a)): if a[i]!='-': print(a[i], end='') """ """ def sum(a): a = str(a) p = 0 for i in range(len(a)): p = p + int(a[i]) return p a = input() while(True): if int(a) >= 10: a = sum(a) else: print(a) break """ """ def sum(a): a = str(a) p = 0 for i in range(len(a)): p = p + int(a[i]) return p k = int(input()) for i in range(k+1): a = input() while (True): if int(a) >= 10: a = sum(a) else: print(a) break """ """ def sum(a): a = a.split() p = 0 for i in range(len(a)): if int(a[i])%5==0: p = p + int(a[i]) return p k = input() a = input() s = 0 s = sum(a) print(s) """ """ k = input() a = input().split() s = 0 for i in range(len(a)): if int(a[i])%2==0: s = s+1 print(s) """ """ a, b = input().split() a = float(a) b = float(b) x = (a-100)*0.9 y = (b-x)*100/x if y <= 10: print("정상") elif 10 < y <= 20: print("과체중") else: print("비만") """ """ def rec(a): if a==0: return print(a) rec(a-1) a = int(input()) rec(a) """
def sum(a): s = 0 for i in range(1,a+1): s = s + i return s