
# slower version:

s = input()
for i in range(len(s)):
  if i%2 == 0:
    print(s[i], end = '')


# optimized version of the same code:

s = input()
ans = ''
for i in range(len(s)):
  if i % 2 == 0:
    ans += s[i]
print(ans)



# slower version:

print((eval(input())))

# optimized version of the same code:

print(eval(input()))
print((eval(input())))

print(eval(input()))

-print((eval(input()))) +print(eval(input()))