5148: Math
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Description
Give you n number $a_{1},a_{2},\cdots,a_{n}$, for all i, j (1 ≤ i ≤ j ≤ n), calculate the sum of $a_{i}\ast a_{j}$.
Input
For each input, the first line is a number n ($n < 100000$).
The second line has n number $a_{1},a_{2},\cdots,a_{n}$, ($a_{i}<1000$).
The second line has n number $a_{1},a_{2},\cdots,a_{n}$, ($a_{i}<1000$).
Output
Print the sum of $a_{i}\ast a_{j}$. ($1\leqslant i\leqslant j\leqslant n$).
Sample 1 Input
2
2 3
Sample 1 Output
19