Re-Enter on c programe

#include 

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;

  }

  cout << "fib(" << n << ") = " << fib(n) << endl;

  return(0);

}