if3xy9 - Online C++ Compiler & Debugging Tool

#include <bits/stdc++.h>
using namespace std;

double a,b,c;

void init(){
	cout<<"Nhap diem Toan:"<<endl;
	cin>>a;
	cout<<"Nhap diem Van"<<endl;
	cin>>b;
	cout<<"Nhap diem Anh"<<endl;
	cin>>c;

}
void solve(){
    double diemtb= ((a*2)+(b*2)+c)/5;
	if(0<=a<=10&&0<=b<=10&&0<=c<=10){
        if(diemtb>=8)
            cout<<"Gioi";
        else if(diemtb>=6.5)
            cout<<"Kha banh";
        else if(diemtb>=5)
            cout<<"Trung binh";
        else
            cout<<"Yeu";
	}
	else{
    cout<<"Nhap diem Toan:"<<endl;
	cin>>a;
	cout<<"Nhap diem Van"<<endl;
	cin>>b;
	cout<<"Nhap diem Anh"<<endl;
	cin>>c;
	}
}

int main() {
	init();
	solve();
	return 0;
}