foo.c:2:6: warning: return type of 'main' is not 'int' [-Wmain]
    2 | void main()
      |      ^~~~
foo.c: In function 'main':
foo.c:4:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    4 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
foo.c:9:6: warning: 'k' may be used uninitialized in this function [-Wmaybe-uninitialized]
    9 |     k++;
      |     ~^~
foo.c:6:2: warning: 'j' may be used uninitialized in this function [-Wmaybe-uninitialized]
    6 | {for (m=2;m<=j; m++)
      |  ^~~

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