foo.c: In function 'main':
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    6 |  scanf("%d%d%f",&kg,&m,&k);//kg西瓜的重量   m学校送的电   k超出的电的收费单价
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~

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