Euclid's algorithm and Fibonacci numbers and Factorial Pro in C++

Euclid's algorithm

#include 

#include

int gcd (int a, int b) 

{

  int temp;

  while (b != 0) 

  {

    temp = a % b;

    a = b;

    b = temp;

  }

  return(a);

}

int main () 

{

  int x, y;

  cout << "Enter two natural numbers: ";

  cin >> x >> y;

  cout << "gcd(" << x << ", " << y << ") = " << gcd(x,y) << endl;

  return(0);

}

Fibonacci numbers

#include 

#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);

}

Factorial

#include 

#include

int fact (int i) 

{

  int result = 1;

  while (i > 0) 

  {

    result = result * i;

    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 << n << "! = " << fact(n) << endl;

  return(0);

}