Onnenluku

#include <iostream>
using namespace std;
typedef long long ll;

ll f(int n, int k) {
	return (k==0?1:k==1?8:9*4)*((1LL<<n)-k);
}

ll solve(string s) {
	int n = s.size();
	if (n<2) return 0;
	ll res=0;
	for(int i=2; i<n; ++i)res+=f(i,2);
	res += f(n-1,1) * (s[0]-'1');
	for(int i=1; i<n; ++i) {
		if (s[i]=='0') break;
		res += f(n-i-1,0) * (s[i]-'1' - (s[0]<s[i]));
		if (s[i]>s[0]) res+=f(n-i-1,1);
		if (s[i]!=s[0]) {
			char a=s[0],b=s[i];
			if (a>b)swap(a,b);
			for(int j=i+1; ; ++j) {
				if (j==n) {res++;break;}
				char c = s[j];
				if (c>b) {
					res += f(n-j,0);
					break;
				} else if (c==b) {
					res += f(n-j-1,0);
				} else if (c>a) {
					res += f(n-j-1,0);
					break;
				} else if (c==a) {
				} else {
					break;
				}
			}
			break;
		}
	}
	return res;
}

int main() {
	ll a,b;
	cin>>a>>b;
	cout<<solve(to_string(b))-solve(to_string(a-1))<<'\n';
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 1

Verdict: ACCEPTED

Test 3

Group: 1

Verdict: ACCEPTED

Test 4

Group: 1

Verdict: ACCEPTED

Test 5

Group: 1

Verdict: ACCEPTED

Test 6

Group: 2

Verdict: ACCEPTED

Test 7

Group: 2

Verdict: ACCEPTED

Test 8

Group: 2

Verdict: ACCEPTED

Test 9

Group: 2

Verdict: ACCEPTED

Test 10

Group: 2

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: WRONG ANSWER

Test 12

Group: 3

Verdict: WRONG ANSWER

Test 13

Group: 3

Verdict: WRONG ANSWER

Test 14

Group: 3

Verdict: WRONG ANSWER

Test 15

Group: 3

Verdict: WRONG ANSWER