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G. Fibonacci army

time limit per test

2 secondsmemory limit per test

256 megabytesinput

standard inputoutput

standard outputKing Cambyses loves Fibonacci numbers. He has several armies. Today he wants to make a new army for himself and he wants the number of men in this army to be the *n*-th Fibonacci number.

Given *n* you should find *n*-th Fibonacci number. The set of Fibonacci numbers start with *f*_{0} = *f*_{1} = 1 and for each *i* ≥ 2, *f*_{i} = *f*_{i - 1} + *f*_{i - 2}.

Input

Input contains a single integer *n* (1 ≤ *n* ≤ 20).

Output

Write a single integer. The *n*-th Fibonacci number.

Examples

Input

2

Output

2

Input

1

Output

1

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