#include <stdlib.h>
#include <stdio.h>

long int fib(long int n) {
  if (n<=1) {
    return n;
  } else {
    return fib(n-1) + fib(n-2);
  }
}

int main(int arg, char** argv) {
  printf("%ld\n", fib(atol(argv[1])));
  return 0;
}