Submission

Score: 100

User: tha_smith

Problemset: โชว์ของโลมา

Language: cpp

Time: 0.002 second

Submitted On: 2026-03-07 20:37:18

#include <bits/stdc++.h>
using namespace std;
#define ll long long

int main() {
	ios_base::sync_with_stdio(0),cin.tie(0);
	ll N;
	cin >> N;
	if(N==1) {
		cout << 1;
	}
	else if(N==2) {
		cout << 7;
	}
	else if(N==3) {
		cout << 24;
	}
	else {
		ll CN=2*N,sum=0,ans=0,track=2;
		for(ll i=2; i<N; i++) {
			if(i%2==0) {
				CN += (N-track);
				sum += CN+CN+1;
				ans += (CN%10) + ((CN+1)%10);
				CN += (N-track);
			}
			else {
				CN += (N-track);
				sum += CN+CN+1;
				CN += (N-track);
				track+=2;
			}
		}
		if(N%2==0) {
			ans += ((N*N)%10) + (((N*N)-1)%10);
		}
		else {
			ans += (N*N)%10;
		}
		cout << ans;
	}
}