s, = gets.split
a = s[0]
b = s[1]
c = s[2]
d = s[3]

count_a = 0
count_a += 1 if a == b
count_a += 1 if a == c
count_a += 1 if a == d

count_b = 0
count_b += 1 if b == a
count_b += 1 if b == c
count_b += 1 if b == d

count_c = 0
count_c += 1 if c == a
count_c += 1 if c == b
count_c += 1 if c == d

count_d = 0
count_d += 1 if d == a
count_d += 1 if d == b
count_d += 1 if d == c

ok = count_a == 1 && count_b == 1 && count_c == 1 && count_d == 1

puts ok ? 'Yes' : 'No'
