CF145D Lucky Pair

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

The first line contains an integer $ n $ $ (2

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.

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.