int fastfib(int n)
{
  int now,next,i,tmp;
        
  if(n <= 0){
    return(0);
  }else if(n == 1){
    return(1);
  }else{
    now  = 1;                   //fastfib(1)=1
    next = 1;                   //fastfib(2)=1

    for(i=3;i<=n;i++){
      tmp   = now;
      now   = next; 
      next += tmp;
    }
  }
  return(next);
}
