/in/foo.cc: In function 'int main()':
/in/foo.cc:16:27: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
         for (i=0;i<L;i++) gets(I[i]);   
                           ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:46,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:16:36: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
         for (i=0;i<L;i++) gets(I[i]);   
                                    ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:46,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/in/foo.cc:20:27: warning: array subscript has type 'char' [-Wchar-subscripts]
                 if (f[n[0]]++) break; //err: used variable
                           ^
/in/foo.cc:31:32: warning: array subscript has type 'char' [-Wchar-subscripts]
                 f[S.top().first]=0;
                                ^
/in/foo.cc:37:43: warning: array subscript has type 'char' [-Wchar-subscripts]
         while (!S.empty()) f[S.top().first]=0, S.pop(); 
                                           ^
/tmp/ccDpzIL7.o: In function `main':
foo.cc:(.text.startup+0xab): warning: the `gets' function is dangerous and should not be used.