/in/foo.cc: In function 'void BFS()':
/in/foo.cc:22:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int k=0;k<ep.size();k++)
                 ~^~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:53:5: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(mat[i]);
     ^~~~
In file included from /usr/include/c++/6/cstdio:42:0,
                 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:53:16: warning: 'char* gets(char*)' is deprecated [-Wdeprecated-declarations]
     gets(mat[i]);
                ^
In file included from /usr/include/c++/6/cstdio:42:0,
                 from /in/foo.cc:1:
/usr/include/stdio.h:640:14: note: declared here
 extern char *gets (char *__s) __wur __attribute_deprecated__;
              ^~~~
/tmp/ccwkAeT5.o: In function `main':
foo.cc:(.text.startup+0x5e): warning: the `gets' function is dangerous and should not be used.