#include<iostream>
using namespace std;
int func()
{
    //...
}
int main()
{
    //...
}

#include<iostream>
using namespace std;
int main()
{
    func();
}
int func()
{
    //...
}

#include<iostream>
using namespace std;
int func()
{
    //...
}
int main()
{
    func();
}

#include<iostream>
using namespace std;
int func();
int main()
{
    func();
}
int func()
{
    //...
}