/in/foo.cc: In function 'int check(int)':
/in/foo.cc:39:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:10:6: warning: 'mid' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int mid;
      ^~~
/in/foo.cc:27:10: warning: 'mid' may be used uninitialized in this function [-Wmaybe-uninitialized]
  if(a[las]!=a[c]-tar) las++;
     ~~~~~^
/in/foo.cc:10:6: note: 'mid' was declared here
  int mid;
      ^~~