Score Calculation

Interview

Time limit1sMemory limit128 MB

Summary

Compute a total score from a 0/1 sequence where consecutive correct answers score an increasing running count.

Level: Easy2 of 10
Topics: Array, Simulation, Implementation
Solved: No attempts yet

Problem

An OX problem has only two possible results: correct or incorrect. In a test made of several OX problems, consecutive correct answers receive bonus points as follows. If problem 1 is correct, it is worth 1 point. After one or more incorrect answers, the first correct answer is also worth 1 point. In a consecutive run of correct answers, the second correct answer is worth 2 points, the third is worth 3 points, and so on, so the K-th correct answer in that run is worth K points. An incorrect answer is worth 0 points.

For example, suppose 10 OX problems are marked with 1 for a correct answer and 0 for an incorrect answer. The scores are calculated as shown below, and the total score is 1+1+2+3+1+2=10.

Result	1	0	1	1	1	0	0	1	1	0
Score	1	0	1	2	3	0	0	1	2	0

Given the grading results of the test, write a program that calculates the total score after applying the bonus rule.

Input

The first line contains the number of problems N (1 <= N <= 100). The second line contains N grading results, each either 0 or 1, separated by spaces. A 0 means the answer was incorrect, and a 1 means the answer was correct.

Output

Print the total score after applying the bonus rule to the grading results from the input.

Examples1

Example 1
Input
```
10
1 0 1 1 1 0 0 1 1 0
```
Expected output
```
10
```