#include <cstdio>
using namespace std;

int a,b,c,k,i;
int main()
{
    FILE *f,*g;
    f=fopen("kfib.in","rt");
    g=fopen("kfib.out","wt");
    fscanf(f,"%d",&k);
    a=b=1;
    for(i=3;i<=k;i++)
    {
        c=(a+b);
        a=b;
        b=c;
    }
    fprintf(g,"%d",b);
    return 0;
}