#include <iostream>
using namespace std;

int fib(int n)
{
  int i, fi, fim1, fim2;

  if (n == 0 || n == 1) return 1;
  
  i = 2;
  fi = 2;
  fim1 = 1;
  fim2 = 1;
  
  while (i < n) {
    i++;
    fim2 = fim1;
    fim1 = fi;
    fi = fim1 + fim2;
  }
  return fi;
}

main()
{
  int n;
 
  cout << "Enter n: ";
  cin >> n;
  cout << "Fib(" << n << ") = " << fib(n) << "." << endl;
  return 0;
}