s1 = input()
l = list(s1)
count_4 = l.count('4')
count_7 = l.count('7')
if((count_4+count_7) == 4 or (count_4+count_7) == 7):
print('YES')
else:
print("NO")
1613B - Absent Remainder | 1536B - Prinzessin der Verurteilung |
1699B - Almost Ternary Matrix | 1545A - AquaMoon and Strange Sort |
538B - Quasi Binary | 424A - Squats |
1703A - YES or YES | 494A - Treasure |
48B - Land Lot | 835A - Key races |
1622C - Set or Decrease | 1682A - Palindromic Indices |
903C - Boxes Packing | 887A - Div 64 |
755B - PolandBall and Game | 808B - Average Sleep Time |
1515E - Phoenix and Computers | 1552B - Running for Gold |
994A - Fingerprints | 1221C - Perfect Team |
1709C - Recover an RBS | 378A - Playing with Dice |
248B - Chilly Willy | 1709B - Also Try Minecraft |
1418A - Buying Torches | 131C - The World is a Theatre |
1696A - NIT orz | 1178D - Prime Graph |
1711D - Rain | 534A - Exam |