Submission #20901681

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Source Code Expand

#include <bits/stdc++.h>

#include <atcoder/all>
#include <boost/multiprecision/cpp_int.hpp>

using namespace std;
using namespace atcoder;
namespace mp = boost::multiprecision;
#define REP(i, m, n) for (int i = (int) (m); i < (int) (n); ++i)
#define rep(i, n) REP(i, 0, n)
using ll = long long;
#define pint pair<int, int>
#define pll pair<ll, ll>
const int inf = 1e9 + 7;
const ll longinf = 1LL << 60;
const ll mod = 1e9 + 7;

using Bint = mp::cpp_int;
using mint = modint998244353;

ll p[16];

int main() {
	p[0] = 1;
	rep(i, 15) {
		p[i + 1] = p[i] * 10;
	}
	ll n;
	cin >> n;
	ll d = 0;
	ll temp = n;
	while (temp) {
		d++;
		temp /= 10;
	}
	//cout << d << endl;
	if (d <= 3) {
		cout << 0 << endl;
		return 0;
	} else if (4 <= d && d < 7) {
		cout << n - p[3] + 1 << endl;
		return 0;
	} else if (7 <= d && d < 10) {
		cout << 2 * (n - p[6] + 1) + (p[6] - p[3]) << endl;
	} else if (10 <= d && d < 13) {
		cout << 3 * (n - p[9] + 1) + (p[6] - p[3]) + 2 * (p[9] - p[6]) << endl;
	} else {
		cout << 4 * (n - p[12] + 1) + (p[6] - p[3]) + 2 * (p[9] - p[6]) +
					3 * (p[12] - p[9]) + (d==16?1:0)
			 << endl;
	}
	return 0;
}

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