Belajar Struct C++

#include <iostream>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
using namespace std;

struct persegi{
int sisi;
};
persegi masuk(void){
persegi psg;
cout<<"Masukkan Sisi : ";cin>>psg.sisi;
return psg;
}
void tampil(persegi a){
cout<<a.sisi*a.sisi;

}

int main(int argc, char** argv) {
persegi b;
b=masuk();
tampil(b);

return 0;
}