Iterative Fibonacci algorithm giving me a wrong result after fib(47)

Question

I am using the iterative fib algorithm that I have copied below. I have found this algorithm on Rosetta code and it gives me the correct answer up until fib(46). After that

Answer 1

You have to use long long also for fnow, fnext, and tempf, try:

long long int fnow = 0, fnext = 1, tempf;