foo.cc: In function ‘void solve()’:
foo.cc:40:39: error: return-statement with a value, in function returning ‘void’ [-fpermissive]
   40 |                     cout << 6; return 0;
      |                                       ^
foo.cc: In function ‘int search(int&, int&)’:
foo.cc:25:1: warning: control reaches end of non-void function [-Wreturn-type]
   25 | }
      | ^