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ile=int(input())
plisz=input().split()
ppo=0
dpo=0
plisz2=[]
for i in range(len(plisz)):
    plisz[i]=int(plisz[i])
    plisz2.append(plisz[i])

for i in range(1,len(plisz)):
    if plisz[i]<=plisz[i-1]:
        if i%2==0:
            ppo+=1
            plisz[i]=100000000
    if plisz[i]>=plisz[i-1]:
        if i%2==1:
            ppo+=1
            plisz[i]=-1000000000000
for i in range(1,len(plisz)):
    if plisz[i]<=plisz[i-1]:
        if i%2==1:
            dpo+=1
            plisz[i]=100000000
    if plisz[i]>=plisz[i-1]:
        if i%2==0:
            dpo+=1
            plisz[i]=-1000000000000
print(min(ppo,dpo))