using System;

public class Program

{

        static int fibonachi(int last)

{

int last_num = last;

int fibonachi_num1 = 0;

int fibonachi_num2 = 1;

int fibonachi_num3 = 1;

int fibonachi_last_num = 0;

for (int i=0; i<last_num - 3; i++)

{

fibonachi_num1=fibonachi_num2;

fibonachi_num2=fibonachi_num3;

fibonachi_num3=fibonachi_num1+fibonachi_num2;

fibonachi_last_num=fibonachi_num3;

}

return fibonachi_last_num;

}

public static void Main()

{

Console.Write("Введіть число");

int last=int.Parse(Console.ReadLine());

int a_num=fibonachi(last);

Console.WriteLine(a_num);

}

}