foo.c: In function 'main':
foo.c:9:11: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
     if (a >= b & a >= c)
         ~~^~~~
foo.c:11:16: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
     else if (b >= a & b >= c)
              ~~^~~~
foo.c:13:16: warning: suggest parentheses around comparison in operand of '&' [-Wparentheses]
     else if (c >= a & c >= b)
              ~~^~~~
foo.c:8:5: 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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