Comment convertir du langage de programmation c++. en c

#include <iostream>

using namespace std;

int main(){
    cout << "Vos deux entiers? ";
    int a, b;
    cin >> a >> b;
    while (not(a >= 0 and b >= 0)) {
        cout << "Retapez? ";
        cin >> a >> b;
    }
    int p = a * b;
    cout << a << "*" << b << endl;
    int s = 0;
    while (b > 0) {
        if (b % 2 == 1) {
            b -= 1;
            s += a;
        } else {
            a *= 2;
            b /= 2;
        }
        cout << " = " << a << "*" << b << " + " << s << endl;
    }
    cout << " = " << s << endl;
    if (s != p) {
        cout << "OUPS.... calcul errone" << endl;
    }
    return 0;
}