int Water( void ) {
    int x,y,s=0,flag;
    for( y=0; y<N-0; y++ ) for( x=0; x<N-0; x++ ) b[y][x]=a[y][x];
    for( y=1; y<N-1; y++ ) for( x=1; x<N-1; x++ ) a[y][x]=N*N;

    do {
      flag = 0;
      for( y=1; y<N-1; y++ ) {
        for( x=1; x<N-1; x++ ) {
          int c = a[y][x];
          int d = Max( b[y][x], Min( Min(a[y+0][x-1],a[y+0][x+1]), Min(a[y-1][x+0],a[y+1][x+0]) ) );
          if( c>d ) a[y][x]=d, flag=1;
        }
      }
    } while( flag );

    for( y=1; y<N-1; y++ ) for( x=1; x<N-1; x++ ) s+=(a[y][x]-b[y][x]);
    return s;
  }