#include <iostream>
#include <stdio.h>
using namespace std;
FILE*f=fopen("nunta.in","r");
FILE*g=fopen("nunta.out","w");
int main()
{
    short f1=1,f2=1,f3;
    int n;
    fscanf(f,"%d",&n);
    while(n){
        f3=f2+f1;
        f1=f2;
        f2=f3;
        n--;
    }
    fprintf(g,"%d",f1);
    fclose(f);
    fclose(g);
    return 0;
}