bt1,2,3,4

// BT1
#include<iostream>
using namespace std;

int main()
{
    cout<<" hello world ";
    return 0;
}
// BT2
#include<iostream>
using namespace std;

int main()
{
    int a,b;
    cout<<" Nhap gia tri a : ";
    cin>>a;
    cout<<" Nhap gia tri b : ";
    cin>>b;
    a-b;
    a+b;
    a/b;
    a*b;
    cout<<" a+b="<<a+b<<endl;
    cout<<" a-b="<<a-b<<endl;
    cout<<" a/b="<<a/b<<endl;
    cout<<" a*b="<<a*b<<endl;
    return 0;
}
// BT3
#include<iostream>
using namespace std;
int main(){
    float a;
    cout<< "\nnhap so : ";
    cin>>a;
    a=int(a);
    cout <<" \nphan nguyen cua so thuc la : "<<int(a);


    return 0;

}
// BT4
#include<iostream>
using namespace std;

int main(){
 char a;
 cout<<" nhap ki tu:";
 cin>>a;
 a=int(a);
 cout<<" ma ASCII : "<<int(a)<<endl;

 return 0;
}