#include <bits/stdc++.h>

using namespace std;
ifstream fin("kfib.in");
ofstream fout("kfib.out");
int main()
{
    long n,i,a,b,c;
    fin>>n;
    if(n==1||n==2)cout<<"1";
    else
    {
        a=1;
        b=1;
        for(i=3;i<=n;++i)
        {
            c=a+b;
            a=b;
            b=c;
        }
       fout<<c;
    }
    return 0;
}