import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines
import numpy as np

N, X = map(int, readline().split())
A = list(map(int, read().split()))
K = 10 ** 5

low = []
high = []
for x in A:
    if x <= K:
        low.append(x)
    else:
        high.append(x)

L = len(low)
H = len(high)

dpl = [None] * (L + 1)
dpl[0] = np.zeros(1, np.int64)
for i, x in enumerate(low, 1):
    dp = np.full(len(dpl[i - 1]) + x, -1, np.int32)
    dp[:-x] = dpl[i - 1]
    dp[x:][dpl[i - 1] >= 0] = i
    dpl[i] = dp

dph = np.zeros(1 << H, np.int64)
for i, x in enumerate(high):
    dph[1 << i: 1 << i + 1] = dph[: 1 << i] + x

nums = X - dph
nums = nums[(0 <= nums) & (nums < len(dpl[-1]))]
nums = nums[dpl[-1][nums] >= 0]

if not len(nums):
    print('No')
    exit()

low_sum = nums[0]
high_sum = X - low_sum

# 復元
low_ind = []
high_ind = []
n = len(low)
while low_sum:
    n = dpl[n][low_sum] - 1
    low_sum -= A[n]
    low_ind.append(n)

i = np.where(dph == high_sum)[0]
for j in range(H):
    if i & (1 << j):
        high_ind.append(j)

nums = [low[i] for i in low_ind] + [high[i] for i in high_ind]
for x in nums:
    i = A.index(x)
    A[i] = 0

answer = ''.join('x' if x else 'o' for x in A)
print(answer)