//     compile with: R CMD SHLIB count2.c
// load into R with: dyn.load("count2.so")
// call from R with: .C("count2", n = as.integer(10), sum = integer(1))

void count2(int *xin, int *sumout)
{
    int x = xin[0];
    int sum = 0;
    for (int i = 1; i <= x; i++)
        sum += i;
    sumout[0] = sum;
}