函数调用

```cpp
#include<iostream>
using namespace std;
void fun(int x, int y);
int main()
{
	int x = 4, y = 7;
	fun(x, y);
	cout << x << "," << y << endl;
	return 0;
}
void fun(int x, int y)
{
	x = x + y;
	y = x - y;
	x = x - y;
	cout << x << "," << y << endl;
}