##### Canadian Computing Competition: 2015 Stage 1, Senior #1

Your boss has asked you to add up a sequence of positive numbers to determine how much money your company made last year.

Unfortunately, your boss reads out numbers incorrectly from time to time.

Fortunately, your boss realizes when an incorrect number is read and says "zero", meaning "ignore the current last number."

Unfortunately, your boss can make repeated mistakes, and says "zero" for each mistake.

For example, your boss can say "One, three, five, four, zero, zero, seven, zero, zero, six", which means the total is 7 as explained in the following chart.

Boss statement(s) | Current numbers | Explanation |
---|---|---|

"One, three, five, four" | 1, 3, 5, 4 | Record the first four numbers. |

"zero, zero" | 1, 3 | Ignore the last two numbers. |

"seven" | 1, 3, 7 | Record the number 7 at the end of our list. |

"zero, zero" | 1 | Ignore the last two numbers. |

"six" | 1, 6 | We have read all numbers, and the total is 7. |

At any point, your boss will have said at least as many positive numbers as "zero" statements. If all positive numbers have been ignored, the sum is zero.

Write a program that reads the sequence of boss statements and computes the correct sum.

#### Input Specification

The first line of input contains the integer which is the number of integers (including "zero") your boss will say. On each of the lines, there will either be one integer between and (inclusive) or the integer .

#### Output Specification

The output is one line, containing the integer which is the correct sum of the integers read, taking the "zero" statements into consideration. You can assume that the output will be an integer in the range and (inclusive).

#### Sample Input 1

```
4
3
0
4
0
```

#### Sample Output 1

`0`

#### Sample Input 2

```
10
1
3
5
4
0
0
7
0
0
6
```

#### Sample Output 2

`7`

## Comments

Will 0 ever be the 1st number?

No, the Boss doesn't have any possible mistakes to erase yet. The Boss's power is only able to skip back up to the amount of positive numbers given. It just works.

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np fam

it says "One, five, three, four, zero, zero, seven, zero, zero, six" on the top but in the chart it says "One, three, five, four"

Fixed, thanks!

There's a typo: "...many positiven umbers as..." should be changed to "...many positive numbers as..."

Fixed, thanks!