Summa

#include <cstdint>
#include <bits/stdc++.h> // wtf
 
/*
 
for first in range(1, 1001):
	for second in range(1, 1001-first-1):
		for third in range(1, 1001-first-second):
			if not set([first, second, third]) in doneSets:
				print repr([first, second, third]), first+second+third, first, second, third
				while True:
					pass
n = 1000 + 1
 
for n in range(3, 1001):
	counter = 0
	doneSets = []
	for first in range(1, n):
		if first == second:
			continue
		for second in range(1, n-first-1):
			for third in range(1, n-first-second):
				if second == third or first == third:
					continue
				kek = set([first, second, third])
				if not kek in doneSets:
					doneSets.append(kek)
					if sum(kek) == (n-1):
						counter += 1
	print n-1, counter
 
n = 1000
for first in range(1, n-1):
 
k = 0
d = 2
i = 8
 
damn = [0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 4, 5, 7, 8]
 
for x in range(14, 1001):
	if k < 4:
		i += d
		k += 1
	elif k == 4:
		i += d + 1
		k += 1
	elif k == 5:
		i += d
		k = 0
		d += 1
	print x, i
	damn.append(i)
 
 
*/
 
std::vector<uint64_t> values = {0, 0, 0, 0, 0, 0, 1, 1, 2, 3, 4, 5, 7, 8};
 
int main() {
	uint64_t n;
	std::cin >> n;
 
	if (n < 14) {
		std::cout << values[n] << std::endl;
		return 0;
	}
 
	uint64_t k = 0;
	uint64_t d = 2;
	uint64_t i = 8;
 
	uint64_t result = 0;
	for (uint64_t x = 14; x <= n; ++x) {
		if (k < 4) { i += d; k += 1; }
		else if (k == 4) { i += d + 1; k += 1; }
		else if (k == 5) { i += d; k = 0; d += 1; }
		result = i;
	}
 
	std::cout << result << std::endl;
 
	return 0;
}
 

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED

Test 7

Verdict: ACCEPTED

Test 8

Verdict: ACCEPTED

Test 9

Verdict: ACCEPTED

Test 10

Verdict: ACCEPTED

Test 11

Verdict: ACCEPTED

Test 12

Verdict: ACCEPTED

Test 13

Verdict: ACCEPTED

Test 14

Verdict: ACCEPTED

Test 15

Verdict: ACCEPTED

Test 16

Verdict: ACCEPTED

Test 17

Verdict: ACCEPTED

Test 18

Verdict: ACCEPTED

Test 19

Verdict: ACCEPTED

Test 20

Verdict: ACCEPTED

Test 21

Verdict: ACCEPTED

Test 22

Verdict: ACCEPTED

Test 23

Verdict: ACCEPTED

Test 24

Verdict: ACCEPTED

Test 25

Verdict: ACCEPTED

Test 26

Verdict: ACCEPTED

Test 27

Verdict: ACCEPTED

Test 28

Verdict: ACCEPTED