Kyselyt

#include <iostream>
#include <string>
using namespace std;

typedef long long ll;

ll p(int n, int x) {
	return x == 0 ? 1 : n*p(n, x-1);
}

int main() {
	int const MAGICAL_CONSTANT = 17;
	ll t[MAGICAL_CONSTANT];
	ll s[MAGICAL_CONSTANT];
	ll a = 0;
	for (int i{0}; i<MAGICAL_CONSTANT; i++) {
		t[i] = p(10, i) * 9 * (i+1);
		a += t[i];
		s[i] = a;
	}

//	for (int i{0}; i<MAGICAL_CONSTANT; i++) {
//		cout << t[i] << endl;
//	}
//	for (int i{0}; i<MAGICAL_CONSTANT; i++) {
//		cout << s[i] << endl;
//	}
	ll n;
	cin >> n;

	if (n < 10) {
		cout << n;
		return 0;
	}

	int c = 0;									// n of digits sorta
	for (int i{0}; i<MAGICAL_CONSTANT; i++) {
		if (s[i] < n) {
			c++;
		}
	}
	ll f = s[c-1];								// count of numDIGITSbers smaller than
//	int d = to_string(n).length();				// n of digits
	ll r = p(10,c);

//	cout << c << endl;
//	cout << r << endl;
	ll temp = n-f;					// much doff
//	cout << temp << endl;
	ll m = temp%(c+1);				// digits already built
	r += temp/(c+1);				// number we are building
//	cout << r << endl;
	if (m == 0) {
		r -= 1;
	}

	r /= p(10,c-m);
	r %= 10;

	cout << r << endl;

//	cout << f << endl;
//	cout << m << endl;							// digit of tha number
//	cout << m << endl;
//	cout << n << " " << c;
	return 0;
}

Test 1

Group: 1

Verdict: WRONG ANSWER

Test 2

Group: 2

Verdict: WRONG ANSWER

Test 3

Group: 3

Verdict: WRONG ANSWER