For Without Init and Update Expressions

Source: Phước Hưng OJ

Version: Phuoc Hung OJ Extended

Problem Statement

Initialize i=0 before the loop; use for (;i<n;) with an increment in the body to sum integers 0 through n-1.

Input

One integer 0<=n<=1000.

Output

The sum from 0 through n-1.

Subtasks

• Subtask 1 (20%): n<=10.
• Subtask 2 (30%): n<=100.
• Subtask 3 (50%): n<=1000.

Examples

Example 1

Input

5

Output

10

Explanation

0+1+2+3+4=10.

Example 2

Input

0

Output

0

Explanation

The loop body never executes.