I made a very simple program to better grasp recursion but something is confusing me.

Question

#include <iostream>
using namespace std;

//a function using recursion to add up numbers in a sequence
int add(int a) {
if (a == 1||a == 2) {
return a + add(a+1);
} else {
return 1;
}

}

int main()
{
cout << add(1);
}

Why is the output 4 rather than 6?
In the first loop or "run" where a = 1, from my point of view it executes like so:
return 1 + 2 = 3
The second and final loop where the parameter is 2:
return 3 + 3(2+1)
Apologies if my layout is confusing but please help

Answer 1

1+ (1+2)

Answer 2

1 + 2 + 1
1 and 2 are the values of a. When a become 3 the loop returns 1