func_code_string: #include <bits/stdc++.h>   using ::std::cin;   using ::std::cout;   using ::std::string;   using ::std::vector;   int binpow(int a, int n) {     if (n == 0) return 1;     if (n % 2 == 0) {       int b = binpow(a, n / 2);       return b * b;     } else       return binpow(a, n - 1) * a;   }   int main() {     int n, l, r;     cin >> n >> l >> r;     cout << binpow(2, l) + n - l - 1 <<              << binpow(2, r) - 1 + (n - r) * binpow(2, r - 1);   }   