add two numbers in c++

#include<iostream>
using namespace std;
int main()
{
	double number1,number2;
  	double sum0;
  	sum=number1+number2;
  	cout<<sum;
}#include <iostream>
using namespace std;

//function declaration
int addition(int a,int b);

int main()
{
	int a,b;	//to store numbers
	int add;	//to store addition 
	
	//read numbers
	cout<<"Enter first number: ";
	cin>>a;
	cout<<"Enter second number: ";
	cin>>b;
	
	//call function
	add=addition(a,b);
	
	//print addition
	cout<<"Addition is: "<<add<<endl;
	
	return 0;
}

//function definition
int addition(int a,int b)
{
	return (a+b);
}