foo.c: In function 'main':
foo.c:9:5: warning: 'main' is normally a non-static function [-Wmain]
 int main()
     ^~~~
foo.c:49:1: error: expected declaration or statement at end of input
 }
 ^
foo.c:5:6: warning: unused variable 'a' [-Wunused-variable]
  int a[505][505];
      ^
foo.c:6:10: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  int m,n;scanf("%d%d",&m,&n);
          ^~~~~~~~~~~~~~~~~~~
At top level:
foo.c:9:5: warning: 'main' defined but not used [-Wunused-function]
 int main()
     ^~~~

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