easy

#include<iostream>
using namespace std;
int qsum(int x)
{
    int sum;
    if(x < 10){sum = x%10;}
    else if(x < 100){sum = x%10+x/10%10;}
    else if(x < 1000){sum = x%10+x/10%10+x/100%10;}
    else if(x == 1000){sum = 1;}
    return sum;
}
int main()
{
    int a,b,sum = 0;
    cin >> a >> b;
    for(int i = a;i <= b;i++){sum += qsum(i);}
    cout << sum << "\n";
    return 0;
}