# Problem C

Code Cleanups

Rather than investing a lot of time figuring out why this degradation in productivity occurred, the line manager suggests that they loosen their requirement: developers can push code that weakly violates the guidelines as long as they run cleanup phases on the code from time to time to make sure the repository is tidy.

She suggests a metric where the “dirtiness” of a developer’s
code is the sum of the pushes that violate the guidelines –
so-called *dirty* pushes – made by that developer, each
weighted by the number of days since it was pushed. The number
of days since a dirty push is a step function that increases by
one each midnight following the push. Hence, if a developer has
made dirty pushes on days $1$, $2$, and $5$, the dirtiness on day $6$ is $5+4+1=10$. She suggests that a
cleanup phase, completely fixing all violations of the coding
guidelines, must be completed before the dirtiness reaches
$20$. One of the
developers, Petra, senses that this rule must be obeyed not
only because it is a company policy. Breaking it will also
result in awkward meetings with a lot of concerned managers who
all want to know why she cannot be more like Perikles? Still,
she wants to run the cleanup phase as seldomly as possible, and
always postpones it until it is absolutely necessary. A cleanup
phase is always run at the end of the day and fixes every dirty
push done up to and including that day. Since all developers
are shuffled to new projects at the start of each year, no
dirtiness should be left after midnight at the end of new
year’s eve.

## Input

The first line of input contains an integer $n$ ($1 \leq n \leq 365$), the number of dirty pushes made by Petra during a year. The second line contains $n$ integers $d_1, d_2, \ldots , d_ n$ ($1 \leq d_ i \leq 365$ for each $1 \le i \le n$) giving the days when Petra made dirty pushes. You can assume that $d_ i < d_ j$ for $i < j$.

## Output

Output the total number of cleanup phases needed for Petra to keep the dirtiness strictly below $20$ at all times.

Sample Input 1 | Sample Output 1 |
---|---|

5 1 45 65 84 346 |
4 |

Sample Input 2 | Sample Output 2 |
---|---|

3 310 330 350 |
3 |