foo.cc: In function 'int main()':
foo.cc:21:11: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
      scanf("%d %s %d %f",&s[i].num,s[i].sname,&s[i].sex,&s[i].score);
      ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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