func_code_string: #include <bits/stdc++.h>   void answer(unsigned long long v) { std::cout << v <<   n ; }   void solve(unsigned n, unsigned k) {     const auto s = n * (n - 1ull) / 2;     if (k > n / 2) return answer(s);     const auto m = n - 2 * k;     const auto d = m * (m - 1ull) / 2;     answer(s - d);   }   int main() {     unsigned n, k;     std::cin >> n >> k;     solve(n, k);     return 0;   }   