灵神模板
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 31, M = 110;
int a, b, n;
int memo[N][M];
int dfs(string& s, int i, int left, bool is_limit, bool is_num) {
if (i == s.size()) {
if (is_num) return left % n == 0;
return 1;
}
if (!is_limit && is_num && memo[i][left] != -1) return memo[i][left];
int res = 0;
if (!is_num) res += dfs(s, i+1, 0, false, false);
int low = is_num ? 0 : 1;
int up = is_limit ? s[i] - '0' : 9;
for (int j = low; j <= up; j++) {
res += dfs(s, i+1, (left + j) % n, is_limit && j == up, true);
}
if (!is_limit && is_num) memo[i][left] = res;
return res;
}
int main() {
while (cin >> a >> b >> n) {
if (a > b) swap(a, b);
string s = to_string(a-1);
memset(memo, -1, sizeof memo);
int r1 = dfs(s, 0, 0, true, false);
s = to_string(b);
memset(memo, -1, sizeof memo);
int r2 = dfs(s, 0, 0, true, false);
cout << r2 - r1 << endl;
}
return 0;
}