foo.cc: In function 'int main()':
foo.cc:14:23: warning: statement has no effect [-Wunused-value]
   14 |    vis[a[i].x][a[i].y]==1;
      |    ~~~~~~~~~~~~~~~~~~~^~~
foo.cc:17:24: warning: statement has no effect [-Wunused-value]
   17 |    vis1[a[i].x][a[i].y]==1;
      |    ~~~~~~~~~~~~~~~~~~~~^~~

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