Kertoma

#include<iostream>
#include<vector>
#include<cmath>
#include<string>

using namespace std;

void pienihaku(vector<long long> v) {
	long long a = 0;
	long long b = 0;
	long long c = 0;
	for (long long i = 0; i < 10; i++) {
		for (long long j = 0; j < v[i]; j++) {
			a += c * pow(10, b);
			b++;
		}
		c++;
	}

	long long x = 2;
	long long y = 2;
	while (y <= a) {
		if (y * (x + 1) <= a) {
			x++;
			y *= x;
		}
		else break;
	}
	cout << x;
}

int main() {
	vector<long long> v(10);
	long long t = 0;
	long long koko = 8;

	for (int i = 0; i < 10; i++) {
		cin >> v[i];
		t += v[i];
	}

	if (t < 18) pienihaku(v);

	else {
		long long x = 2;
		long long numerot = 0;
		long long edellinen = 2;


		while (numerot < t) {
			x++;
			long long y = edellinen * x;
			if (trunc(log10(y)) + 1 > koko) {
				numerot += (trunc(log10(y)) + 1) - koko;
				edellinen = stoll(to_string(y).substr(0, koko));
			}
			else {
				edellinen = y;
				if (trunc(log10(y)) + 1 > numerot) numerot = trunc(log10(y)) + 1;
			}
		}

		cout << x;
	}
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

Test 6

Group: 1, 2, 3

Verdict: ACCEPTED

Test 7

Group: 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: ACCEPTED

Test 9

Group: 2, 3

Verdict: ACCEPTED

Test 10

Group: 2, 3

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED

Test 16

Group: 3

Verdict: ACCEPTED