Represents first and last numbers of each type ( modulo 0 and 1 )
let L = new Array ( 3 ) ; let R = new Array ( 3 ) ; L [ l % 2 ] = l ; R [ r % 2 ] = r ; l ++ ; r -- ; if ( l <= tR && r >= tL ) { L [ l % 2 ] = l ; R [ r % 2 ] = r ; }