Utility to generate gamp data file from a ROOT tree
Author: Yi Qiang <yqiang@jlab.org>

Usage: root2gamp [options] <input file>
	-H print help messages
	-B save beam information
	-T save target information
	-A append existing file
	-M<events> max number of events processed (default: all)
	-C<config file> specify config file (default: config.txt)
	-O<output file> specify output filename (default: output.gamp)

Configuration file:
The configuration file doesn't support comments at this moment.
And the input parameters have to be listed using the exact order without any empty lines:

Line 1:	name of the ROOT tree;
Line 2:	formula to evaluate the best combo from the save event to save,
	either with maximum or minimum values
Line 3:	branch for beam particle
Line 4:	branch for target particle
Line 5:	number of reconstructed particles
Line 6 and so on: branches of reconstructed particles

Output files:
1.	GAMP file
2.	Index file, first column is the event number,
	second column is the value of the formula used to select the combo.