Compilare: main.cpp: In function 'int solve()': main.cpp:45:19: warning: comparison of integer expressions of different signedness: 'std::stack<int>::size_type' {aka 'long unsigned int'} and 'int' [-Wsign-compare] 45 | if(stk.size() < last) | ~~~~~~~~~~~^~~~~~ main.cpp:25:10: warning: variable 'flag' set but not used [-Wunused-but-set-variable] 25 | bool flag; | ^~~~