what is the remainder when 3 ^ 30 is divided by 5 ?
"the units digit of powers of 3 follow a repeating cycle of four : { 3 , 9 , 7 , 1 } 30 has the form 4 k + 2 , so the units digit of 3 ^ 30 is 9 . the remainder when dividing by 5 is 4 . the answer is e ."
subtract(divide(5, const_2), multiply(3, 3))