#include<stdio.h>
int main ()
{
    freopen("nunta.in","r",stdin);
    freopen("nunta.out","w",stdout);
    int n,i,k,a,b,c;
    scanf("%d",&n);
    a=1;
    b=1;
    for(i=1;i<=n;i++)
    {c=a;
    a+=b;
    b=c;
}
printf("%d\n",a);
return 0;
}