import java.util.Scanner;

public class Calculator
{
    //Sample function you may call to test you input
    public static int fib(int n)
    {
		if (n < 1) 
			return -1;
		if (n < 3)
			return 1;
		int a = 1;
		int b = 1;
		for (int i=2;i<n;i++){
			int tmp = a+b;
			a = b;
			b = tmp;
		}
		return b;
    }
    
    public static void main(String[] args)
    {
		//TODO
    }
}