function mark(elem) {
		elem.style.backgroundColor = '#f1f1f2';
	}
	
	function unmarkAll16() {
		z1.style.backgroundColor = 'white';
		z2.style.backgroundColor = 'white';
		z3.style.backgroundColor = 'white';
		z4.style.backgroundColor = 'white';
		z5.style.backgroundColor = 'white';
		z6.style.backgroundColor = 'white';
		z7.style.backgroundColor = 'white';
		z8.style.backgroundColor = 'white';
		z9.style.backgroundColor = 'white';
		z10.style.backgroundColor = 'white';
		z11.style.backgroundColor = 'white';
		z12.style.backgroundColor = 'white';
		z13.style.backgroundColor = 'white';
		z14.style.backgroundColor = 'white';
		z15.style.backgroundColor = 'white';
		z16.style.backgroundColor = 'white';
	}
	
	function unmarkAll19() {
		z1.style.backgroundColor = 'white';
		z2.style.backgroundColor = 'white';
		z3.style.backgroundColor = 'white';
		z4.style.backgroundColor = 'white';
		z5.style.backgroundColor = 'white';
		z6.style.backgroundColor = 'white';
		z7.style.backgroundColor = 'white';
		z8.style.backgroundColor = 'white';
		z9.style.backgroundColor = 'white';
		z10.style.backgroundColor = 'white';
		z11.style.backgroundColor = 'white';
		z12.style.backgroundColor = 'white';
		z13.style.backgroundColor = 'white';
		z14.style.backgroundColor = 'white';
		z15.style.backgroundColor = 'white';
		z16.style.backgroundColor = 'white';
		z17.style.backgroundColor = 'white';
		z18.style.backgroundColor = 'white';
		z19.style.backgroundColor = 'white';
	}
	
	function unmarkAll24() {
		z1.style.backgroundColor = 'white';
		z2.style.backgroundColor = 'white';
		z3.style.backgroundColor = 'white';
		z4.style.backgroundColor = 'white';
		z5.style.backgroundColor = 'white';
		z6.style.backgroundColor = 'white';
		z7.style.backgroundColor = 'white';
		z8.style.backgroundColor = 'white';
		z9.style.backgroundColor = 'white';
		z10.style.backgroundColor = 'white';
		z11.style.backgroundColor = 'white';
		z12.style.backgroundColor = 'white';
		z13.style.backgroundColor = 'white';
		z14.style.backgroundColor = 'white';
		z15.style.backgroundColor = 'white';
		z16.style.backgroundColor = 'white';
		z17.style.backgroundColor = 'white';
		z18.style.backgroundColor = 'white';
		z19.style.backgroundColor = 'white';
		z20.style.backgroundColor = 'white';
		z21.style.backgroundColor = 'white';
		z22.style.backgroundColor = 'white';
		z23.style.backgroundColor = 'white';
		z24.style.backgroundColor = 'white';
	}
	
	function unmarkAll26() {
		z1.style.backgroundColor = 'white';
		z2.style.backgroundColor = 'white';
		z3.style.backgroundColor = 'white';
		z4.style.backgroundColor = 'white';
		z5.style.backgroundColor = 'white';
		z6.style.backgroundColor = 'white';
		z7.style.backgroundColor = 'white';
		z8.style.backgroundColor = 'white';
		z9.style.backgroundColor = 'white';
		z10.style.backgroundColor = 'white';
		z11.style.backgroundColor = 'white';
		z12.style.backgroundColor = 'white';
		z13.style.backgroundColor = 'white';
		z14.style.backgroundColor = 'white';
		z15.style.backgroundColor = 'white';
		z16.style.backgroundColor = 'white';
		z17.style.backgroundColor = 'white';
		z18.style.backgroundColor = 'white';
		z19.style.backgroundColor = 'white';
		z20.style.backgroundColor = 'white';
		z21.style.backgroundColor = 'white';
		z22.style.backgroundColor = 'white';
		z23.style.backgroundColor = 'white';
		z24.style.backgroundColor = 'white';
		z25.style.backgroundColor = 'white';
		z26.style.backgroundColor = 'white';
	}
	
	function unmarkAll30() {
		z1.style.backgroundColor = 'white';
		z2.style.backgroundColor = 'white';
		z3.style.backgroundColor = 'white';
		z4.style.backgroundColor = 'white';
		z5.style.backgroundColor = 'white';
		z6.style.backgroundColor = 'white';
		z7.style.backgroundColor = 'white';
		z8.style.backgroundColor = 'white';
		z9.style.backgroundColor = 'white';
		z10.style.backgroundColor = 'white';
		z11.style.backgroundColor = 'white';
		z12.style.backgroundColor = 'white';
		z13.style.backgroundColor = 'white';
		z14.style.backgroundColor = 'white';
		z15.style.backgroundColor = 'white';
		z16.style.backgroundColor = 'white';
		z17.style.backgroundColor = 'white';
		z18.style.backgroundColor = 'white';
		z19.style.backgroundColor = 'white';
		z20.style.backgroundColor = 'white';
		z21.style.backgroundColor = 'white';
		z22.style.backgroundColor = 'white';
		z23.style.backgroundColor = 'white';
		z24.style.backgroundColor = 'white';
		z25.style.backgroundColor = 'white';
		z26.style.backgroundColor = 'white';
		z27.style.backgroundColor = 'white';
		z28.style.backgroundColor = 'white';
		z29.style.backgroundColor = 'white';
		z30.style.backgroundColor = 'white';
	}