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#include <bits/stdc++.h>

using namespace std;

int count(vector<int> &num, bool up){
    int cnt=0;
    bool changed=false;
    
    for(int i=0;i<num.size()-1;++i){
        if(up){
            if(num[i]<num[i+1] || changed){
                changed = false;
                //cout<<"UP ";
            }
            else{
                cnt++;
                changed =true;
                //cout<<"CHANGEDUP ";
            }
        }
        else{
            if(num[i] > num[i+1] || changed){
                changed = false;
                //cout<<"DOWN ";

            }
            else{
                cnt++;
                changed = true;
                //cout<<"CHANGEDOWN ";

            }
        }
        up = !up;
    }
    return cnt;
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    int n; cin>>n;
    vector<int> nums(n);
    for(auto &x : nums) cin>>x;
    cout<<min(count(nums, false), count(nums,true))<<'\n';

    return 0;
}