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#include <bits/stdc++.h>

using namespace std;

int main()
{
    std::ios_base::sync_with_stdio(0);
    std::cin.tie(nullptr);
    std::cout.tie(nullptr);
    int n, w1=0, w2=0;
    cin>>n;
    int t[n];
    for(int i=0; i<n; ++i)
        cin>>t[i];
    vector <char> s;
    s.push_back(0);
    for(int i=0; i<n-1; ++i)
    {
        if(t[i+1]>t[i])
            s.push_back('W');
        if(t[i+1]<t[i])
            s.push_back('M');
        if(t[i+1]==t[i])
            s.push_back('R');
    }
    s.push_back(0);
    vector <char> s2;
    s2=s;
    for(int i=1; i<n; ++i)
    {
        if(i%2==1)
        {
            if(s[i]=='W' || s[i]=='R')
            {
                if(s[i+1]=='M' || s[i+1]=='R')
                    s[i+1]='W';
                s[i]='M';
                ++w1;
            }
        }
        else
        {
            if(s[i]=='M' || s[i]=='R')
            {
                if(s[i+1]=='W' || s[i+1]=='R')
                    s[i+1]='M';
                s[i]='W';
                ++w1;
            }
        }
    }
    for(int i=1; i<n; ++i)
    {
        if(i%2==1)
        {
            if(s2[i]=='M' || s2[i]=='R')
            {
                if(s2[i+1]=='W' || s2[i+1]=='R')
                    s2[i+1]='M';
                s2[i]='W';
                ++w2;
            }
        }
        else
        {
            if(s2[i]=='W' || s2[i]=='R')
            {
                if(s2[i+1]=='M' || s2[i+1]=='R')
                    s2[i+1]='W';
                s2[i]='M';
                ++w2;
            }
        }
    }
    cout<<min(w1, w2);
    return 0;
}