#include<iostream>
using namespace std;
int main()

{
    int a, b, c, d;
    cout<<"Hay nhap so thu nhat : ";
    cin>>a;
    cout<<"Hay nhap so thu hai : ";
    cin>>b;
    cout<<"Hay nhap so thu ba : ";
    cin>>c;
    cout<<"Hay nhap so thu tu : ";
    cin>>d;
    //tong = a+b+c+d;
    cout<<"Chu so hang don vi cua tong cac so da nhap la : "<<(a+b+c+d)%10;

}