Joseph , the primary school teacher of Illinois Public School , distributed some sweets among the students of his class on his birthday . After distributing three sweets to every student, he found some sweets were still left over with him . He doubled the number of sweets with each student and found that he still had M sweets left over. However, instead of doubling, had he given only one sweet extra to every student , he would have been left with N sweets `(N gt M)`. How many students are there is his class ?