procedure quartersearch (x : inter, a1, a2, ?, an) : increasing integers) i := 1{i is left endpoint of search interval} ? j := n {j is right endpoint of search interval} while i < j begin m :=? ?(i + j)? / 4 if x am then ?i := m+1 else if x am then ?m : = ?(i + j)? / 4 else if x am then m := 2 ?(i + j)? /4 else ?if x am then m := 3 ?(i + j)? /4 else j := m end if x = ai then location := i else location := 0