Arjun and Fibonacci

We all know the famous Fibonacci series where F(0) = 0, F(1) = 1 and F(n) = F(n-1) + F(n-2) According to Arjun, the shortest way to write the code for the above series is as follows: long long fibonacci(int n) { if (n==0) return 0; if (n==1) return 1; return fibonacci(n-1) + fibonacci(n-2); } But he observed that the program is too slow for practical purposes. Having learnt about recursions and