Climbing Stairs

Problem statement

A learner climbs a staircase with n steps. On each move the learner climbs either one step or two steps. Count all ordered sequences of moves that finish exactly at the top; two sequences differing in move order are different.

Input format

One integer n.

Output format

Print the number of possible move sequences.

Constraints

1 <= n <= 45.

Sample input

1

Sample output

1