Main.cpp: In function 'bool is_valid(std::string)':
Main.cpp:12:19: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
12 | for(register int i = 0; i < (int)s.size(); ++i){
| ^
Main.cpp: In lambda function:
Main.cpp:31:20: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
31 | for(register int i = 1; i <= n; ++i){
| ^
Main.cpp:40:20: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
40 | for(register int i = 1; i <= n; ++i){
| ^
Main.cpp:66:20: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
66 | for(register int i = 0; i < (n << 1); ++i){
| ^
Main.cpp:72:21: warning: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
72 | for(register int i = 1; i <= n; ++i){
| ^
Main.cpp:29:20: warning: unused variable 'closings' [-Wunused-variable]
29 | int openings(0), closings(0);
| ^~~~~~~~