Calculate powers of a number in C++

#include <iostream>
using namespace std;
int main()
{
    int a , b , r=1;
    cout << "Enter a number (a)" << endl;
    cin >> a;
    cout << "Enter its power (b)" << endl;
    cin >> b;
    while (b>0)
    {
        b=b-1;
        r=r*a;
    }
    cout << endl << "a^b = " << r;
}