from collections import deque

N, K = map(int, input().split())
S = input()

D = deque()

for i in range(K):
    D.append(S[i])

flag = True
res = []

for i in range(N - K):
    if flag:
        s = D.pop()
        res.append(s)
        flag = False
        D.appendleft(S[K + i])
    else:
        s = D.popleft()
        res.append(s)
        flag = True
        D.append(S[K + i])

for i in range(K):
    if flag:
        s = D.pop()
        res.append(s)
    if not flag:
        s = D.popleft()
        res.append(s)

print(''.join(res))