A seer was scheduled to visit a village in the month of January but the date was not fixed. The village head wanted to offer him as many grams of gold as the date of the visit. So he went to the goldsmith, told his intention and asked him to make 31 different gold coins each weighing from 1 to 31 grams - so that he could offer the appropriate coin on the day of the visit. The goldsmith was an intelligent person and pondered for a while. He told the village head that only 5 coins of different denominations would suffice. With combinations from them, the total weight matching any date can be arrived at. What should be the weight of each of the 5 coins ?