/in/foo.cc: In function 'int solve()':
/in/foo.cc:33:22: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
     if (j & (1 << k) == 1) {
             ~~~~~~~~~^~~~
/in/foo.cc:21:6: warning: unused variable 'c1' [-Wunused-variable]
  int c1, c2, c3, c4, tot;
      ^~
/in/foo.cc:21:10: warning: unused variable 'c2' [-Wunused-variable]
  int c1, c2, c3, c4, tot;
          ^~
/in/foo.cc:21:14: warning: unused variable 'c3' [-Wunused-variable]
  int c1, c2, c3, c4, tot;
              ^~
/in/foo.cc:21:18: warning: unused variable 'c4' [-Wunused-variable]
  int c1, c2, c3, c4, tot;
                  ^~
/in/foo.cc:49:1: warning: no return statement in function returning non-void [-Wreturn-type]
 }
 ^
/usr/lib/gcc/x86_64-linux-gnu/6/../../../x86_64-linux-gnu/Scrt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status