Number of possible paths using combinations

By how many ways can robot reach to its destination?

according to diagram there are 28 ways .But how?

at current position robot can have atmost 6 RIGHT MOVES & 2 DOWN MOVES.

RRRRRRDD

So answer is nothing but total ways in which RRRRRRDD can be arranged

and formula for that is nCr(8)/((nCr(6))*(nCr(2))) which is 28

unsigned int factorial(unsigned int n)
{
     if(n == 0)
          return 1;
    unsigned int i = n, fact = 1;
    while (n / i != n)
    {
        fact = fact * i;
        i--;
    }
    return fact;
}



int uniquePaths(int m, int n){
    return (factorial(m+n-2))/((factorial(m-1))*(factorial(n-1)));
}