dan

#include <iostream>
using namespace std;
void f(int &a, int b)
{a=2*a;
b=2*b;
cout<<"a="<<a<< " b="<<b<<endl;
}
int main()
{int x=1,y=2;
cout<<"x="<<x<<" y="<<y<<endl;
f(x,y);
cout<<"x="<<x<<" y="<<y<<endl;
    return 0;
}