编写四个重载函数Double（x），返回值为输入参数的两倍；参数类型分别为int，long，float，double，返回值类型与参数类型一致。

#include<iostream>
using namespace std;

int Double(int x);
long Double(long x);
float Double(float x);
double Double(double x);

int main()
{
int myInt = 6500;
cout<<Double(myInt)<<endl;
long myLong = 65000;
cout<<Double(myLong)<<endl;
float myFloat = 6.5F;
cout<<Double(myFloat)<<endl;
double myDouble = 6.5e20;
cout<<Double(myDouble)<<endl;
}

int Double(int x)
{
return 2*x;
}
long Double(long x)
{
return 2*x;
}
float Double(float x)
{
return 2*x;
}
double Double(double x)
{
return 2*x;
}