A - Sum of Digits (15-12)

#include <bits/stdc++.h>
#define int64_t long long
using namespace std;

int a, b;
int64_t dp[20][180][2];
vector<int> digit;

void getDigits(int x) {
    digit.clear();
    while(x) {
        digit.push_back(x % 10);
        x /= 10;
    }
}

int64_t digitSum(int id, int sum, bool tight) {
    if(id == -1) return sum;

    if(dp[id][sum][tight] != -1 && !tight)
        return dp[id][sum][tight];

    int64_t res = 0;
    int k = (tight) ? digit[id] : 9;

    for(int i = 0; i <= k; ++i) {
        int newTight = tight & (digit[id] == i);
        res += digitSum(id - 1, sum + i, newTight);
    }

    if(!tight)
        dp[id][sum][tight] = res;

    return res;
}

int main() {
#ifdef DN
    freopen("in.txt", "r", stdin);
#endif
    //freopen("CPCRC1C.inp", "r", stdin);
    //freopen("CPCRC1C.out", "w", stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(NULL); cout.tie(NULL);

    while(cin >> a >> b) {
        if(a == -1 && b == -1) break;

        fill(**dp, **dp + 20 * 180 * 2, -1);
        getDigits(a - 1);
        int64_t ans1 = digitSum(digit.size()-1, 0, true);

        fill(**dp, **dp + 20 * 180 * 2, -1);
        getDigits(b);
        int64_t ans2 = digitSum(digit.size()-1, 0, true);

        cout << ans2 - ans1 << '\n';
    }

    return 0;
}