#include <stdio.h>
void fibo( short int  n, short int a ,short  int b )
{
  for (;n;n--)
  {
      short int aux=a;
       a+=b;
       b=aux;
  }
}
int main()
{
     freopen("nunta.in","r",stdin);
    freopen("nunta.out","w",stdout);
    char fib1[500],fib2[500];
    short int a,b,n;
      scanf("%d",&n);
      a=1; b=1;
     if( n==1 ) printf("%d",1);
     else
    {
    fibo(n,a,b);
    printf("%d",b);
     }

    return 0;
}