foo.cc: In function 'int main()':
foo.cc:17:51: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    if(stu[i][4]<stu[j][4] || stu[i][4]==stu[j][4] &&stu[i][1]<stu[j][1] || stu[i][4]==stu[j][4] && stu[i][1]==stu[i][4] && stu[i][0]>stu[j][0])
                              ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
foo.cc:17:121: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
    if(stu[i][4]<stu[j][4] || stu[i][4]==stu[j][4] &&stu[i][1]<stu[j][1] || stu[i][4]==stu[j][4] && stu[i][1]==stu[i][4] && stu[i][0]>stu[j][0])
                                                                            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
foo.cc:6:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ~~~~~^~~~~~~~~
foo.cc:9:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d",&stu[i][1],&stu[i][2],&stu[i][3]);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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