输入四个整数，找出其中最大的数，用一个函数来实现

例4.4

#include <iostream>
using namespace std;
int max(int, int);
int max_four(int, int, int, int);
int main() {
	int a, b, c, d;
	cout << "请输入四个整数：";
	cin >> a >> b >> c >> d;
	int max = max_four(a, b, c, d);
	cout << "这四个数中最大的是：" << max << endl;
	return 0;
}

int max(int a, int b) {
	int max = (a > b) ? a : b;
	return max;
}

int max_four(int a, int b, int c, int d) {
	int max(int, int);
	int m = max(a, b);
		m = max(m, c);
		m = max(m, d);
	return m;
}