Nth Triangular Number

Nth Triangular Number

Compute the Nth triangular number by recursion.

Input format

A single line with one integer N (N >= 1).

Output format

Print the Nth triangular number T(N) = 1 + 2 + ... + N.

Constraints

• Values fit in a 64-bit signed integer
• Trailing whitespace and a trailing newline are ignored by the judge

Read from stdin, write to stdout. Sample cases below show the exact format.

1

1

2

3