Lucky Number 2
题目描述
Petya loves lucky numbers very much. Everybody knows that lucky numbers are positive integers whose decimal record contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not.
Petya loves long lucky numbers very much. He is interested in the minimum lucky number d that meets some condition. Let cnt(x) be the number of occurrences of number x in number d as a substring. For example, if d=747747, then cnt(4)=2, cnt(7)=4, cnt(47)=2, cnt(74)=2. Petya wants the following condition to fulfil simultaneously: cnt(4)=a1, cnt(7)=a2, cnt(47)=a3, cnt(74)=a4. Petya is not interested in the occurrences of other numbers. Help him cope with this task.
The single line contains four integers a1, a2, a3 and a4 (1≤a1,a2,a3,a4≤106).
On the single line print without leading zeroes the answer to the problem − the minimum lucky number d such, that cnt(4)=a1, cnt(7)=a2, cnt(47)=a3, cnt(74)=a4. If such number does not exist, print the single number "-1" (without the quotes).
2 2 1 1
4774
4 7 3 1
-1
题目来源：fps-www.educg.net-codeforce-1-2833.xml.zip；FPS 共享题包，题包内第 2670 题。保留原作者与原赛事署名。