im trying to merge 3 root files using hadd. these are three files

```
56847850 Jan 27 14:41 ElectronBver2_35_2.root
60978397 Jan 27 15:11 ElectronBver2_35.root
64647820 Jan 27 15:42 ElectronBver2_36_3.root
```

i try to merge them like

`hadd -f ElectronB_ver2.root ElectronBver2_35.root ElectronBver2_35_2.root ElectronBver2_36_3.root`

which gives me this output

```
hadd compression setting for all output: 1
hadd Source file 1: ElectronBver2_35.root
hadd Source file 2: ElectronBver2_35_2.root
hadd Source file 3: ElectronBver2_36_3.root
hadd Target path: ElectronB_ver2.root:/
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed65d29bf0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed65e341a0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed65d3c3d0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed65cca000)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed65215900)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed65179af0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed6519f8b0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed66fc8ec0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed66fcfc40)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed66fd69c0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed66fdd740)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed66fe44c0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed66feb240)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed66ff1fc0)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed66ffac80)
Error in <TObjArray::At>: index 835 out of bounds (size: 835, this: 0x55ed67001940)
```

the number of events in the target file is equal to the sum of events in each source file. But im not sure about the error. i see this, which suggest error message `can be ignored`

.

Can i ignore this error or is there any solution?

Im using lxplus with ROOT 6.30/02

Regards