foo.cc: In function 'int main()':
foo.cc:115:8: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
   mid=l+r>>1;
       ~^~
In file included from /usr/include/string.h:494:0,
                 from /usr/include/c++/7/cstring:42,
                 from foo.cc:3:
In function 'void* memcpy(void*, const void*, size_t)',
    inlined from 'void fun(int*, int, int, int)' at foo.cc:26:8,
    inlined from 'bool check(int)' at foo.cc:79:5,
    inlined from 'int main()' at foo.cc:116:11:
/usr/include/x86_64-linux-gnu/bits/string_fortified.h:34:71: warning: 'void* __builtin___memcpy_chk(void*, const void*, long unsigned int, long unsigned int)' writing 24 bytes into a region of size 12 overflows the destination [-Wstringop-overflow=]
   return __builtin___memcpy_chk (__dest, __src, __len, __bos0 (__dest));
                                                                       ^

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。