A group of 500 students went to the college canteen and ordered some items. 285 students ordered ice-cream, 195 students ordered cold coffee, 115 students ordered cold drink, 45 students ordered ice-cream and cold drink, 70 students ordered cold coffee and ice-cream, 50 students ordered cold coffee and cold drink, and 50 students did not order anything. Find the number of students who ordered all three items.
