/in/foo.cc: In function 'int main()':
/in/foo.cc:23:14: warning: 'y' may be used uninitialized in this function [-Wmaybe-uninitialized]
   x1=a[x+1][y]>a[x-1][y]? x+1:x-1;
      ~~~~~~~~^
/in/foo.cc:25:14: warning: 'x' may be used uninitialized in this function [-Wmaybe-uninitialized]
   sum+=a[x][y]+a[x][y1]+a[x1][y]+a[x1][y1];
        ~~~~~~^