[C++]: Calculadora

#include <iostream>
#include <Windows.h>
using namespace std;

double div(double x, double y);
double more(double x,double y);
double sub(double x,double y);
double mul(double x,double y);

void Restart();

int main(){
    double x,y,ans;
    int mode;

    cout << "O que deseja fazer?\n[1] Soma\n[2] Divisao\n[3] Multiplicacao\n[4] Subtracao \n";
    cin >> mode;
    if(mode == 1){
        mode = 0;

        cout << "Numero1: ";
        cin >> x;

        cout << "Numero2: ";
        cin >> y;

        ans = more(x,y);

        cout << "Resultado: " << ans << endl;
        Sleep(10000);
        Restart();
    }
    else if(mode == 2){
        mode = 0;

        cout << "Numero1: ";
        cin >> x;

        cout << "Numero2: ";
        cin >> y;

        ans = div(x,y);

        cout << "Resultado: " << ans << endl;
        Sleep(10000);
        Restart();
    }
    else if(mode == 3){
        mode = 0;

        cout << "Numero1: ";
        cin >> x;

        cout << "Numero2: ";
        cin >> y;

        ans = mul(x,y);

        cout << "Resultado: " << ans << endl;
        Sleep(5000);
        Restart();
    }
    else if(mode == 4){
        mode = 0;

        cout << "Numero1: ";
        cin >> x;

        cout << "Numero2: ";
        cin >> y;

        ans = sub(x,y);

        cout << "Resultado: " << ans << endl;
        Sleep(5000);
        Restart();

    }
    else {
        cout << "Opcao errada." << endl;
        Sleep(5000);
        system("CLS");
        main();
    }

    return 0;
}

double div(double x, double y){ return x/y; }
double more(double x,double y){ return x+y; }
double sub(double x,double y){ return x-y; }
double mul(double x,double y){ return x*y; }

void Restart(){
    int r;

    cout << " " << endl;
    cout << "Escolha a opcao: \n[1] Fechar aplicativo\n[2] Restar Aplicativo \n";
    cin >> r;

    if(r == 1) { system("EXIT"); }
    else if(r == 2) { system("CLS"), main(); }
    else { system("CLS"), Restart(); }
}