829 B | 829 chars
import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta
# sys.setrecursionlimit(10**7)
BLANK = " "
# inp = input
inp = lambda : sys.stdin.readline().rstrip()
mii = lambda x = BLANK : [*map(int,inp().split(x))]
mfi = lambda x = BLANK : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
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)
INF = 1e19
def solve():
d = [INF for _ in range(60)]
d[0] = 0
d[3] = 1
d[5] = 1
n = ii()
for i in range(6, 60):
d[i] = 1 + min(d[i - 3], d[i - 5])
if n in [1, 2, 4, 7]:
p(-1)
else:
if n < 60:
p(d[n])
else:
p(d[n % 15 + 15] + (n // 15 - 1) * 3)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
ret = solve()