def solve(s):
    if not s:
        return ''
    dic = {}
    for i in s:
        dic[i] = dic.get(i, 0) + 1
    dic = sorted(dic.items(), key=lambda x: x[0])
    res = ''
    for i in dic:
        res += i[0]
        res += str(i[1])
    return res

if __name__ == '__main__':
    s = input()
    print(solve(s))