1151: 累加和

Memory Limit:128 MB Time Limit:1.000 S
Judge Style:Text Compare Creator:
Submit:52 Solved:37

Description

用高精度方法,求 s=1+2+3+……+n 的精确值(1<=n<=106)。 

Input

输入n的值

Output

输出高精度的和值

Sample Input Copy

10

Sample Output Copy

55