fib.c

#include <stdio.h>
int fib(n){                                                                     
  if (n < 2) return n;                                                          
  else return fib(n-2) + fib(n-1);                                              
} 
                                                                                
int main(){                                                                     
  int n = 39;                                                                   
  printf("39 : %d\n", fib(n));                                                  
}