what is the units digit of 31 ! + 50 ! + 2 ! + 3 ! ?
"for all n greater than 4 , the units digit of n ! is 0 . the sum of the four units digits is 0 + 0 + 2 + 6 = 8 the units digit is 8 . the answer is e ."
add(add(const_4, const_3), const_2)