#include <stdio.h> int print(int n) { int count = 0; int sum = 0; for (int i = 1; count < n; i++) { for (int j = 1; j <= i; j++) { sum += i; count++; if (count == n) break; } } return sum; } int main() { int a; while (scanf("%d", &a) != EOF) { // 注意 while 处理多个 case // 64 位输出请用 printf("%lld") int ret = print(a); printf("%d\n", ret); } return 0; }