Tinky Winky left a sequence of zeroes in the Tubbytronic Superdome, and left for a walk with Dipsy. When he came back, he saw that a misdeed has been done. The sequence was changed, and Po was smiling mischeviously in the corner of the room.

*Oh dear! Po, what have you done?!* – asked Tinky Winky in horror.

*I enhanced the sequence!* – replied Po.

After cross-examination, it was established that Po did a number of enhancements on the sequence. In every enhancement, she took a **segment** of a sequence and **increased** all elements in the segment by some positive integer. Also, every two segments were either disjoint or one was completely contained in other.

*How many enhancements have you done, Po?* – Laa-Laa inquired.

*I really don't know! I'm only sure I did the minimum number of enhancements possible to get this sequence!* – said Po exhaustedly.

*Then it surely must be !* – proclaimed Noo-Noo.

What number did Noo-Noo say?

#### Input Specification

The first line contains an integer , the length of the sequence.

The second line contains non-negative integers , the sequence after Po's enhancements.

#### Output Specification

Output , the minimum possible number of enhancements.

#### Constraints

Subtask | Points | Constraints |
---|---|---|

1 | 30 | |

2 | 40 | No additional constraints. |

#### Sample Input 1

```
3
2 2 2
```

#### Sample Output 1

`1`

#### Sample Input 2

```
5
2 3 3 3 2
```

#### Sample Output 2

`2`

#### Explanation for Sample Output 2

Po first increased all elements of the sequence by , and then increased the middle three by .

#### Sample Input 3

```
6
1 2 3 2 1 3
```

#### Sample Output 3

`4`

## Comments