import sys
input = sys.stdin.readline

ANS=[]
S="ABCDEFGHIJKLMNOPQRSTUVWXYZ"

for i in range(26):
    if i>=1:
        ANS.append(S[0]+S[i])

    ANS.append(S[i]+S[i])

    if i>=1:
        for j in range(1,i):
            ANS.append(S[i]+S[j])
            ANS.append(S[j]+S[i])

    if i>=1:
        ANS.append(S[i]+S[0])

for ans in ANS:
    print(ans)