program combin
tempfile cp
tempvar k
gen `k'=1
quietly save "`cp'"
rename `1' `1'1
forv i=2/`2' {
	joinby `k' using "`cp'"
	rename `1' `1'`i'
	quietly drop if `1'`i'<=`1'`=`i'-1'
}
sort `1'*
end