mod = 1000000007
eps = 10**-9


def main():
    import sys
    input = sys.stdin.readline

    S = input().rstrip('\n')
    T = "abcdefghijklmnopqrstuvwxyz"

    for i in range(26):
        if S[i]!= T[i]:
            print(T[i] + "to" + S[i])
            break

if __name__ == '__main__':
    main()