
# 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:

def main():

	n, ma, mb, *L = list(map(int, open(0).read().split()))

	M = 1<<30

	dp = [[M] * 420 for _ in range(420)]

	dp[0][0] = 0

	for a, b, c in zip(*[iter(L)] * 3):

		for i in range(400, -1, -1):

			for j in range(400, -1, -1):

				t = dp[i][j] + c

				if dp[i + a][j + b] > t:

					dp[i + a][j + b] = t

	ans = M

	_ma, _mb = ma, mb

	while _ma < 410 > _mb:

		ans = min(ans, dp[_ma][_mb])

		_ma += ma

		_mb += mb

	print((ans if ans < M else -1))



if __name__=="__main__":

	main()

# optimized version of the same code:

def main():

	n, ma, mb, *L = list(map(int, open(0).read().split()))

	M = 1 << 30

	dp = [[M] * 420 for _ in range(420)]

	dp[0][0] = 0

	ua = ub = 15

	for a, b, c in zip(*[iter(L)] * 3):

		for i in range(ua, -1, -1):

			for j in range(ub, -1, -1):

				t = dp[i][j] + c

				if dp[i + a][j + b] > t:

					dp[i + a][j + b] = t

					if ua < i + a:

						ua = i + a

					if ub < j + b:

						ub = j + b

	ans = M

	_ma, _mb = ma, mb

	while _ma < 410 > _mb:

		ans = min(ans, dp[_ma][_mb])

		_ma += ma

		_mb += mb

	print((ans if ans < M else -1))





if __name__ == "__main__":

	main()

def main():
    n, ma, mb, *L = list(map(int, open(0).read().split()))
    M = 1 << 30
    dp = [[M] * 420 for _ in range(420)]
    dp[0][0] = 0
    for a, b, c in zip(*[iter(L)] * 3):
        for i in range(400, -1, -1):
            for j in range(400, -1, -1):
                t = dp[i][j] + c
                if dp[i + a][j + b] > t:
                    dp[i + a][j + b] = t
    ans = M
    _ma, _mb = ma, mb
    while _ma < 410 > _mb:
        ans = min(ans, dp[_ma][_mb])
        _ma += ma
        _mb += mb
    print((ans if ans < M else -1))


if __name__ == "__main__":
    main()

def main():
    n, ma, mb, *L = list(map(int, open(0).read().split()))
    M = 1 << 30
    dp = [[M] * 420 for _ in range(420)]
    dp[0][0] = 0
    ua = ub = 15
    for a, b, c in zip(*[iter(L)] * 3):
        for i in range(ua, -1, -1):
            for j in range(ub, -1, -1):
                t = dp[i][j] + c
                if dp[i + a][j + b] > t:
                    dp[i + a][j + b] = t
                    if ua < i + a:
                        ua = i + a
                    if ub < j + b:
                        ub = j + b
    ans = M
    _ma, _mb = ma, mb
    while _ma < 410 > _mb:
        ans = min(ans, dp[_ma][_mb])
        _ma += ma
        _mb += mb
    print((ans if ans < M else -1))


if __name__ == "__main__":
    main()

+    ua = ub = 15 -        for i in range(400, -1, -1): -            for j in range(400, -1, -1): +        for i in range(ua, -1, -1): +            for j in range(ub, -1, -1): +                    if ua < i + a: +                        ua = i + a +                    if ub < j + b: +                        ub = j + b