为什么重载函数有问题

#include <iostream>
using namespace std;
int max(int a,int b)
{
    if (a < b)return b;
    else return a;
}
double max(double a,double b)
{
    if (a < b)return b;
    else return a;
}
int main()
{
    float m, n;
    int x, y;
    cin >> x >> y;
    cout << max(x, y);
    cin >> m>> n;
    cout << max(m, n);
    return 0;

为什么没法重载函数