n = 26
a = list("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
g = [[True]*n for i in range(n)]
g[25][0] = False

ans = []
# a-z の 26頂点間を、S=a,T=z で移動 (z-aだけ取り除く)

def directed_euler_dfs(i,trail,n,g):
  for j in range(n):
    if g[i][j]:
      g[i][j] = False
      directed_euler_dfs(j,trail,n,g)
  trail.append(i)

directed_euler_dfs(0,ans,n,g)
ans.reverse()
#print(g)

for i in range(n*n-1):
  print(f"{a[ans[i]]}{a[ans[i+1]]}")
print("ZA")