992 B | 981 chars
"""
[29283: Алекс и стейк](https://www.acmicpc.net/problem/29283)
Tier: Bronze 3
Category: arithmetic, math
"""
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
SYS_INPUT = True
RECURSION_LIMIT = 10 ** 7
SET_RECURSION = False
BLANK = " "
if SET_RECURSION:
sys.setrecursionlimit(RECURSION_LIMIT)
inp = lambda : sys.stdin.readline().rstrip() if SYS_INPUT else input()
mii = lambda : [*map(int,inp().split())]
mfi = lambda : [*map(float,inp().split())]
ii = lambda : int(inp())
fi = lambda : float(inp())
isplit = lambda : inp().split()
p = print
def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)
def solve():
k = ii()
mx_cnt = (k - 1) // 5 + 1
last = k % 5
if last == 0:
last = 5
idx = mx_cnt - 1
ans = idx * (idx + 1) // 2 * 5 * 30
ans += last * mx_cnt * 30
p(ans)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()