вычислить сумму нечетных элементов массива С++

int a[] = { 1,3,4,6,5,7,1,2,4,5,7,8,9,1,4,3,0,1,4,2,5,7,8 };
const size_t size = sizeof(a) / sizeof(int);
double sum = 0;
unsigned n = 0;
do if (~a[n] & 1) sum += a[n]; while (++n < size);
cout << " Sum = " << sum << endl;