import sys

L = sys.stdin.read().splitlines()
S = 0

l = [0, 3, 6, 9, 12, 15] #-3
#l = [1, 3, 6, 10, 15, 21] #0
l = [10, 13, 16, 21, 30, 45]
#l = [-6, -9, -13, -18]
m = list(l)
prem=[]
prem.append(m[0])
print(m)

while not all(v == 0 for v in l):
    m = []
    for i in range(0,len(l)-1):
        m.append(l[i+1] - l[i])
        
    prem.append(m[0])
    print(m)
    l = list(m)

s = prem[0]
signe = -1
for a in prem[1:]:
    s+=(a*signe)
    signe *= -1
print(s)
S+=s
#print(sum(prem))

print(S)