unsigned r = (x %d + y %d) %d;

r = (x mod d + y mod d) mod d;

r1 = x % d;
r2 = y % d;

r = r1 < ( d - r2 ) ? r1 + r2 : r1 - ( d - r2 );

unsigned int remainder(unsigned int x, unsigned int y, unsigned int d)
{
    unsigned int r1 = x % d;
    unsigned int r2 = y % d;

    return r1 < (d - r2) ? r1 + r2 : r1 - (d - r2);
}