foo.c:3:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main()
      ^~~~
foo.c: In function 'main':
foo.c:7:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d%d",&a, &b, &c);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~

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