You can refer this code: https://github.com/latifahkagamecohort/mhl_tree/blob/8cc6898fe593e45e69f8999cec248f43648c1549/add.c

Which is using function like this to sum 10 numbers:

int sum (int a,int b,int c,int d,int e,int f,int g,int h,int i,int j)
{
    return a+b+c+d+e+f+g+h+i+j;
}