#include<stdio.h>

#include<string.h>

int Fib(int n)

{

 int a = 1;

 int b = 1;

 int c = 0;

 while(n>=3)

 {

   c = a+b;

a = b;

b = c;

n--;

 }

  return c;

}

int main()

{  

int n = 0;

int fib = Fib(n);

scanf("%d",&n);

printf("%d\n",Fib);

 return 0;

}