Problem:
Score : 300 points

Problem Statement

In a flower bed, there are N flowers, numbered 1,2,......,N. Initially, the heights of all flowers are 0.
You are given a sequence h=\{h_1,h_2,h_3,......\} as input. You would like to change the height of Flower k to h_k for all k (1 \leq k \leq N), by repeating the following "watering" operation:

Specify integers l and r. Increase the height of Flower x by 1 for all x such that l \leq x \leq r.

Find the minimum number of watering operations required to satisfy the condition.

Constraints

1 \leq N \leq 100

0 \leq h_i \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

N
h_1 h_2 h_3 ...... h_N

Output

Print the minimum number of watering operations required to satisfy the condition.

Sample Input 1

4
1 2 2 1

Sample Output 1

2

The minimum number of watering operations required is 2.
One way to achieve it is:

Perform the operation with (l,r)=(1,3).

Perform the operation with (l,r)=(2,4).

Sample Input 2

5
3 1 2 3 1

Sample Output 2

5

Sample Input 3

8
4 23 75 0 23 96 50 100

Sample Output 3

221

Solution in Python (3.4.3) (judge verdict: Accepted)

import numpy as np

#l,rまでの配列に+1する関数
def give_water(flower, lr):
    flower_with_water = [x+1 if i>=lr[0] and i<=lr[1] else x for i,x in enumerate(flower)]
    return flower_with_water

def TF_list(flower, h):
    h = np.array(h)
    TF_list_0 = []
    for i in range(len(flower)):
        TF_list_0.append(flower[i] < h[i])
    return TF_list_0

#Trueが連続しているindexの範囲を[(0, 1), (2,4)]みたいな形で出力
def list_tuple_True(flower, h, N):
    TF_list = (flower < h)
    TF_list = np.insert(TF_list, N, False)
    True_range = []
    #FLAGは一つ前のTFを表す。初期値はFalse
    FLAG = False
    for i, TF in enumerate(TF_list):
        if TF:
            if FLAG:
                #Trueが連続している場合
                pass
            else:
                #FalseからTrueに切り替わった場合
                start = i
        else:
            if FLAG:
                #TrueからFalseも切り替わった場合
                end = i-1
                True_range.append((start, end))
            else:
                #Falseが連続している場合
                pass
        FLAG = TF
    return True_range
            
N = int(input())
h = list(map(int, input().split()))

h = np.array(h)
flower = np.zeros(N)

count = 0
while not((h == flower).all()):
    water_range = list_tuple_True(flower, h, N)
    count += len(water_range)
    for lr in water_range:
        flower = give_water(flower, lr)
        
print(count)