n = int(input())
ceni = map(int, input().split())
ceni2 = list()
minc = min(ceni)
maxc = max(ceni)
summa = 0
rock = 1
srav = 0
itog = 0
for i in ceni:
summa += i
if summa < maxc:
print(maxc)
else:
for i_ in range(n):
if srav < ceni[i_] and rock == 1:
itog += ceni[i_]
srav = ceni[i_]
else:
itog -= ceni[i_]
srav = ceni[i_]
print(itog)
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