#include <fstream>
#include <iostream>
using namespace std;


int main () {

long long n,a,b,c;

ifstream f("nunta.in");
ofstream g("nunta.out");

f>>n;

a=1; b=1;
 while (a+b<=n) {
                 c=a+b;
                 a=b;
                 b=c;
		  }    
     

cout<<c;

f.close();
g.close();

return 0;

}