1141 : Reverse
Time Limit: 1 Sec Memory Limit: 128 Mb Submitted: 3 Solved: 2Description
Bobo has an n digits decimal number D = d1d2…dn (It may have leading zeros).
Let R(i, j) denotes number D with digits between the i-th position and j-th position reversed.
That is, R(i, j) = d1…di − 1djdj − 1…didj + 1dj + 2…dn.
Bobo would like to find
$$ \sum_{i=1}^{n}\sum_{j=i}^{n}R(i,j) $$
modulo (109 + 7).
Input
The input contains at most 30 sets. For each set:
The first line contains an integer n(1 ≤ n ≤ 105).
The second line contains n digits d1d2…dn(0 ≤ di ≤ 9).
Output
For each set, an integer denotes the result.
Sample
2 12 3 012 10 0123456789
45 369 733424314
Hint
Author
ftiasch