def main():
    import sys
    sys.setrecursionlimit(1000000)
    n, x = map(int, sys.stdin.readline().split())
    a = list(map(int, sys.stdin.readline().split()))
    
    # 预处理：排除所有大于x的元素，并记录它们的索引
    elements = [(a[i], i) for i in range(n) if a[i] <= x]
    m = len(elements)
    if m == 0:
        print("No")
        return
    
    sum_total = sum(num for num, idx in elements)
    if sum_total < x:
        print("No")
        return
    
    # 按降序排列
    elements.sort(reverse=True, key=lambda x: x[0])
    
    # 计算后缀和
    suffix_sum = [0] * (m + 1)
    for i in range(m-1, -1, -1):
        suffix_sum[i] = suffix_sum[i+1] + elements[i][0]
    
    selected = [False] * n
    
    # 回溯函数
    def backtrack(pos, current_sum, path):
        if current_sum == x:
            for idx in path:
                selected[elements[idx][1]] = True
            return True
        if pos >= m:
            return False
        
        # 不选当前元素
        if backtrack(pos + 1, current_sum, path):
            return True
        
        # 选当前元素，如果当前sum + 元素的值 <=x 并且加上后缀和可能达到x
        if current_sum + elements[pos][0] > x:
            return False
        if current_sum + elements[pos][0] + suffix_sum[pos+1] < x:
            return False  # 剪枝
        
        if backtrack(pos + 1, current_sum + elements[pos][0], path + [pos]):
            return True
        return False
    
    found = backtrack(0, 0, [])
    if found:
        s = ''.join('o' if selected[i] else 'x' for i in range(n))
        print(s)
    else:
        print("No")

if __name__ == "__main__":
    main()