foo.cc: In function 'int main()':
foo.cc:33:12: warning: unused variable 'M' [-Wunused-variable]
   33 |       char M,F;
      |            ^
foo.cc:33:14: warning: unused variable 'F' [-Wunused-variable]
   33 |       char M,F;
      |              ^
foo.cc:21:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   21 |  {  scanf("%d %s %d %f",&s[i].num,s[i].name,&s[i].sex,&s[i].score);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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