SUM OF NUMBERS USING RECURSION IN C++

/*QUESTION :
Write a recursive function that computes the sum of all numbers from 1 to n , where n is given as parameter by the user.
*/

//CODE:

#include <iostream>
using namespace std;
int sum(int x);
//MAIN STARTS
int main(){
 cout<<"ENTER A NUMBER : ";
 int a;
 cin>>a;
 cout<<"The required sum is : "<<sum(a)<<endl;

 return 0;
}

// MAIN ENDS
int sum(int x){
 if (x == 1)
  return 1;
 else
  return ( x + sum (x-1));
}