fibonacci number

[Jose M]

Hi, the next code is right. I mean it works. It gives the sequence of fibonaci numbers ...

#include <iostream>
#include <iomanip>
using namespace std;

int fibo(int pos)
{
 
  if(!pos)return 0;
  if(pos==1)return 1;

  int pos2=--pos;
  int pos1=--pos;

  int r1=fibo(pos1);
  int r2=fibo(pos2);

  int r=r1+r2;

  return r;
}

int main()
{

  int number;
  cin>>number;
  
  for(int p=0;p<number;++p)
    {
      int r=fibo(p);
      cout<<p<<"  "<<r<<endl;
    }

  cout<<endl;

  return  0;
}

but....
when I chage the lines:

int r1=fibo(pos1);
  int r2=fibo(pos2);

  int r=r1+r2;

for the lines:

int r=fibo(pos1)+fibo(pos2);

It doen't work right. Apararently it should work the same.
Can anyone give an explanation to this...?????

Thanks