import sys
for line in sys.stdin.readlines():
    line = line.strip()
    ret = {}
    m = len(line)
    min_c = {}
    for c in line:
        ret[c] = line.count(c)
        if ret[c] < m:
            min_c = {c}
            m = ret[c]
        elif ret[c] == m:
            min_c.add(c)
    for c in min_c:
        line = line.replace(c, '')
    print(line)