Lucky Pair

题意翻译

一个正整数是幸运数，当且仅当其在十进制表示下各位数字仅由 $4$ 和 $7$ 组成。比如 $47,44774$ 是幸运数，而 $467$ 不是。 现有一个正整数序列 $a$，你需要找到两个区间 $[l_1,r_1],[l_2,r_2]$，使得 $l_1\le r_1<l_2\le r_2$，且 $a[l_1\cdots r_1]$ 和 $a[l_2\cdots r_2]$ 不包含相同的幸运数字。 求这样的区间对的数量。

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 has an array $ a $ of $ n $ integers. The numbers in the array are numbered starting from $ 1 $ . Unfortunately, Petya has been misbehaving and so, his parents don't allow him play with arrays that have many lucky numbers. It is guaranteed that no more than $ 1000 $ elements in the array $ a $ are lucky numbers. Petya needs to find the number of pairs of non-intersecting segments $ [l_{1};r_{1}] $ and $ [l_{2};r_{2}] $ ( $ 1<=l_{1}<=r_{1}&lt;l_{2}<=r_{2}<=n $ , all four numbers are integers) such that there's no such lucky number that occurs simultaneously in the subarray $ a[l_{1}..r_{1}] $ and in the subarray $ a[l_{2}..r_{2}] $ . Help Petya count the number of such pairs.

输入输出格式

输入格式

The first line contains an integer $ n $ $ (2<=n<=10^{5}) $ — the size of the array $ a $ . The second line contains $ n $ space-separated integers $ a_{i} $ ( $ 1<=a_{i}<=10^{9} $ ) — array $ a $ . It is guaranteed that no more than $ 1000 $ elements in the array $ a $ are lucky numbers.

输出格式

On the single line print the only number — the answer to the problem. Please do not use the %lld specificator to read or write 64-bit integers in С++. It is preferred to use the cin, cout streams or the %I64d specificator.

输入输出样例

输入样例 #1

4
1 4 2 4

输出样例 #1

9

输入样例 #2

2
4 7

输出样例 #2

1

输入样例 #3

4
4 4 7 7

输出样例 #3

9

说明

The subarray $ a[l..r] $ is an array that consists of elements $ a_{l} $ , $ a_{l+1} $ , ..., $ a_{r} $ . In the first sample there are $ 9 $ possible pairs that satisfy the condition: $ [1,1] $ and $ [2,2] $ , $ [1,1] $ and $ [2,3] $ , $ [1,1] $ and $ [2,4] $ , $ [1,1] $ and $ [3,3] $ , $ [1,1] $ and $ [3,4] $ , $ [1,1] $ and $ [4,4] $ , $ [1,2] $ and $ [3,3] $ , $ [2,2] $ and $ [3,3] $ , $ [3,3] $ and $ [4,4] $ . In the second sample there is only one pair of segments — $ [1;1] $ and $ [2;2] $ and it satisfies the condition.