Fibonacci Number C++ Program

#include
// sequence is 0, 1, 1, 2, 3, 5, 8, 13, ...
int fib (int i) {
int pred, result, temp;
pred = 1; result = 0;
while (i > 0)
{
temp = pred + result;
result = pred;
pred = temp;
i = i-1;
}
return(result);
}
int main ()
{
int n;
cout << "Enter a natural number: ";
cin >> n;
while (n < 0)
{
cout << "Please re-enter: ";
cin >> n;
}