if 0 <= X and X < 300 then Y = 3;
if 300 <= X and X < 600 then Y = 6;
if 600 <= X and X < 900 then Y = 9;
if 900 <= X and X < 1200 then Y = 12;
if ..................................
if........................
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.........
if 2700 <= X and X < 3000 then Y = 30;