capture {
	forv i=1/20 {
		forv j=1/20 {
			display "check `i',`j'"
			if el("a",`i',`j')==20 {
				display "found at `i',`j'"
				exit -1
			}
		}
	}
}
if _rc==-1 {
	// value was found
}
else if _rc==0 {
	display "not found"
}
else exit _rc