n, X = map(int, input().split())
A = list(map(int, input().split()))

sum_total = sum(A)
if sum_total < X:
    print("No")
elif sum_total == X:
    print('o' * n)
else:
    found = False
    for i in range(n):
        if A[i] == X:
            s = ['x'] * n
            s[i] = 'o'
            print(''.join(s))
            found = True
            break
    if found:
        exit()

    mask = 1
    for a in A:
        if a > X:
            continue
        mask |= mask << a
        mask &= (1 << (X + 1)) - 1

    if not (mask & (1 << X)):
        print("No")
    else:
        selected = [False] * n
        current_sum = X
        for i in reversed(range(n)):
            a = A[i]
            if a > current_sum:
                continue
            if (mask >> (current_sum - a)) & 1:
                selected[i] = True
                current_sum -= a
                if current_sum == 0:
                    break

        s = []
        for i in range(n):
            s.append('o' if selected[i] else 'x')
        print(''.join(s))