Both sides can only be integer constants, including positive and negative numbers.
2%5 is "2 modulo 5", quotient 0, remainder 2, and result 2.
(-9)%5 is "-9 mod 5", quotient 1, remainder -4, and result -4.
The result of the function mod(n, m) may be different from that of the mod operator.
Mod (-9,5) may get 1.