/in/foo.cc: In function 'void Match(char*)':
/in/foo.cc:47:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i<strlen(s); i++)
                  ~^~~~~~~~~~
/in/foo.cc:51:18: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
   if (s[i] == ')'&&s1.Empty() || s[i] == ')'&&s1.Top() == ')')s1.Push(i, s[i]);
       ~~~~~~~~~~~^~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:62:2: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(s);
  ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/c++/6/ext/string_conversions.h:43,
                 from /usr/include/c++/6/bits/basic_string.h:5417,
                 from /usr/include/c++/6/string:52,
                 from /usr/include/c++/6/bits/locale_classes.h:40,
                 from /usr/include/c++/6/bits/ios_base.h:41,
                 from /usr/include/c++/6/ios:42,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:2:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:62:8: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
  gets(s);
        ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/c++/6/ext/string_conversions.h:43,
                 from /usr/include/c++/6/bits/basic_string.h:5417,
                 from /usr/include/c++/6/string:52,
                 from /usr/include/c++/6/bits/locale_classes.h:40,
                 from /usr/include/c++/6/bits/ios_base.h:41,
                 from /usr/include/c++/6/ios:42,
                 from /usr/include/c++/6/ostream:38,
                 from /usr/include/c++/6/iostream:39,
                 from /in/foo.cc:2:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/tmp/ccUVvjhX.o: In function `main':
foo.cc:(.text.startup+0xe): warning: the `gets' function is dangerous and should not be used.