foo.cc: In function 'int main()':
foo.cc:21:16: warning: operation on 'Mnum' may be undefined [-Wsequence-point]
  Fsum=Fsum=Mnum=Mnum=0;
            ~~~~^~~~~~~
foo.cc:21:6: warning: operation on 'Fsum' may be undefined [-Wsequence-point]
  Fsum=Fsum=Mnum=Mnum=0;
  ~~~~^~~~~~~~~~~~~~~~~
foo.cc:19:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%s%d%f",&s1[i].num,s1[i].name,&s1[i].sex,&s1[i].score);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:38:58: warning: 'Msum' may be used uninitialized in this function [-Wmaybe-uninitialized]
     printf("%.1f\n%.1f\n%.1f\n",Msum/Mnum,Fsum/Fnum,(Msum+Fsum)/n);
                                                     ~~~~~^~~~~~
foo.cc:38:47: warning: 'Fnum' may be used uninitialized in this function [-Wmaybe-uninitialized]
     printf("%.1f\n%.1f\n%.1f\n",Msum/Mnum,Fsum/Fnum,(Msum+Fsum)/n);
                                           ~~~~^~~~~

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