/in/foo.cc:33:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wreturn-type]
 main() {
      ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:41:25: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
             int mid = l + r >> 1;
                       ~~^~~
/in/foo.cc:45:29: warning: 'ans' may be used uninitialized in this function [-Wmaybe-uninitialized]
         printf("%lld\n",ans);
                             ^