solveSlow.cpp

#include <bits/stdc++.h>

typedef int64_t Int;

Int solveSlow(Int n, Int k) {
    if (k > n-k) return solveSlow(n, n-k);
    Int bin = 1;
    for (Int i = 1; i <= k; ++i) {
        bin *= (n - i + 1);
        bin /= i;
    }
    Int count = 1 + (bin != 1);
    for (Int i = 2; i * i <= bin; ++i) {
        Int j = bin / i;
        if (i * j == bin) {
            count += 1 + (j != i);
        }
    }
    return count;
}

int main() {
    std::cout << solveSlow(18, 9) << std::endl;
    return 0;
}