void test(){


	ROOT::RDataFrame df(1000);
	df.Define("dummyA", "1>0")
		.Define("dummyB", "1<0")
		.Snapshot("MYtuple","file1.root");
	ROOT::RDataFrame df2(2000);
	df2.Define("dummyA", "1<0")
		 .Snapshot("MYtuple","file2.root");

	TChain ch("MYtuple");
	ch.AddFile("file1.root");
	ch.AddFile("file2.root");

	// std::cout<< "Chain entries = "<< ch.GetEntries() << std::endl;
	ROOT::RDataFrame dfM( ch);
	dfM.Define("aug", "1>0")
		 .Snapshot("MYtuple","fileMerge.root");


}