
# 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:

_,s=open(c:=0)

for a in sorted(map(int,s.split())):c=a-c

print(c)

# optimized version of the same code:

for a in sorted(map(int,[*open(c:=0)][1].split())):c=a-c

print(c)
_, s = open(c := 0)
for a in sorted(map(int, s.split())):
    c = a - c
print(c)

for a in sorted(map(int, [*open(c := 0)][1].split())):
    c = a - c
print(c)

-_, s = open(c := 0) -for a in sorted(map(int, s.split())): +for a in sorted(map(int, [*open(c := 0)][1].split())):