#include <iostream>
#include <conio.h>
#include <math.h>
using namespace std; // 1. Khai bao thu vien
main ()
{
    float t,l,h,tb;
    do
    {
        cout <<"\nNhap diem toan : "; cin>>t;    
        if ((t<0) || (t>10))
           cout <<"Nhap lai diem toan! \n"; 
    }  
    while ((t<0) || (t>10));
    
    do
    {
        cout <<"\nNhap diem ly : "; cin>>l;    
        if ((l<0) || (l>10))
           cout <<"Nhap lai diem ly! \n"; 
    }  
    while ((l<0) || (l>10));
    
    do
    {    
        cout <<"Nhap diem hoa : "; cin>>h;   
        if ((h<0) || (h>10))
           cout <<"Nhap lai diem hoa! \n";
    }
    while ((h<0) || (h>10));
    
    tb= (t*3 + l*2 +h)/6;
    
    if (tb <5)
       cout << "Rot. Hoc sinh yeu";
    else
        if (tb<7)
           cout <<"Dau. Hoc sinh trung binh";
        else 
             if (tb>8)
                cout<<"Dau. Hoc sinh gioi";
             else 
                  cout <<"Dau. Hoc sinh kha";
      
getch();
}