answer.code: In function ‘int main()’:
answer.code:47:9: error: ‘stack’ was not declared in this scope
   47 |         stack<int> a_stk, d_stk;
      |         ^~~~~
answer.code:11:1: note: ‘std::stack’ is defined in header ‘<stack>’; did you forget to ‘#include <stack>’?
   10 | #include <unordered_map>
  +++ |+#include <stack>
   11 | 
answer.code:47:15: error: expected primary-expression before ‘int’
   47 |         stack<int> a_stk, d_stk;
      |               ^~~
answer.code:50:9: error: ‘a_stk’ was not declared in this scope
   50 |         a_stk.push(0); d_stk.push(0);
      |         ^~~~~
answer.code:50:24: error: ‘d_stk’ was not declared in this scope
   50 |         a_stk.push(0); d_stk.push(0);
      |                        ^~~~~