#include <cstdlib>
#include <iostream>
#include <vector>
using namespace std;

class Fib {  // This is step 2 of dynamic programming: Add a cache.
  public:
    long long find_fib(int n);
    vector <long long> cache;
};

long long Fib::find_fib(int n)   // Create the cache if this is the first call.
{                                // Otherwise, return the answer from the cache if it's there.
  if (cache.size() == 0) cache.resize(n+1, -1);
  if (cache[n] != -1) return cache[n];

  if (n == 0 || n == 1) {        // If it's not in the cache, do the recursion, and put
    cache[n] = 1;                // the answer into the cache before returning.
  } else {
    cache[n] = find_fib(n-1) + find_fib(n-2);
  }
  return cache[n];
}

int main(int argc, char **argv)
{
  Fib f;

  if (argc != 2) { cerr << "usage: fib n\n"; exit(1); }

  cout << f.find_fib(atoi(argv[1])) << endl;
  return 0;
}