$|=1;
$line = <STDIN>;chomp $line;
($N, $H)=split " ",$line;
for($i=0;$i<$N;$i++){
 $line = <STDIN>;chomp $line;
 ($a, $b)=split " ",$line;
 push @A,$a;push @B,$b;
}

$c=0;
while($H>0) {
	$dm=-1;$ai=-1;$bi=-1;
	for($i=0;$i<=$#AA;$i++){ if($dm<$AA[$i]){$dm=$AA[$i];$ai=$i;} }
	for($i=0;$i<=$#B; $i++){ if($dm<$B [$i]){$dm=$B [$i];$bi=$i;} }
	if ($bi>=0) {
		$H=$H-$dm;$c+=1;
		push @AA, $A[$bi];
		splice @A,$bi,1;
		splice @B,$bi,1;
	} else {
		$n=int(($H+$dm-1)/$dm);
		$H=$H-$dm*$n;$c+=$n;
	}
}
print "$c\n";
