#include 
                  int main()
                  {
                    int grade,counter=1,sum=0,e;
                    while(counter<=10)
                    {
                      printf("student grade\"%d\"=",counter);
                      scanf("%d",&grade);
                      if(grade<=100&&grade>=1)
                      {
                        sum+=grade;
                        counter++;
                        e=1;
                      }
                      else
                      {
                        e=0;
                        break;
                      }
                    }
                    if(e==1)
                      printf("class average=%f",sum/(float)(counter-1));
                    else
                      printf("enter real grade");

                    return 0;
                  }