$$ 1 + 2+3 + 18 = 24$$ 
A cat divides $$24$$ cans of tuna into $$4$$ groups. Each group has at least $$1$$ can of tuna, and the number of cans in each group \uline{cannot be the same}. There are at mostcans of tuna in the group that has the largest number of cans. 
  $$6$$ 
  $$18$$ 
  $$21$$ 
  $$24$$ 