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// #pragma GCC optimize("O3")
// #pragma GCC optimize("Ofast")
// #pragma GCC optimize("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#include <bits/stdc++.h>
using namespace std;

#define rep(i, n) for(int i = 0; i < n; i++)
#define pb push_back
#define debug(x) cout << #x << " " << x << endl
#define all(x) x.begin(),x.end()
#define ll long long
#define vi vector<int>
#define vvi vector<vi>
#define vvvi vector<vvi>
#define vll vector<ll>
#define vvll vector<vll>
#define ld long double
#define ull unsigned long long
#define vull vector<ull>
#define fi first
#define se second
#define PII pair<int,int>
#define vPII vector<PII>
#define getunique(v) {sort(v.begin(), v.end()); v.erase(unique(v.begin(), v.end()), v.end());}
#define int128 __int128

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
	cout << setprecision(16) << fixed;
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        int n; cin >> n; vi a(n); rep(i,n) cin >> a[i];
        int ans1 = 0, ans2 = 0;
        int zm = 0;
        for(int i = 1; i < n; i++){
            if(zm){
                zm = 0;
            }else{
                if(i&1){
                    if(a[i] <= a[i-1]){
                        zm = 1;
                        ans1++;
                    }
                }else{
                    if(a[i] >= a[i-1]){
                        zm = 1;
                        ans1++;
                    }
                }
            }
        }
        zm = 0;
        for(int i = 1; i < n; i++){
            if(zm){
                zm = 0;
            }else{
                if(i&1){
                    if(a[i] >= a[i-1]){
                        zm = 1;
                        ans2++;
                    }
                }else{
                    if(a[i] <= a[i-1]){
                        zm = 1;
                        ans2++;
                    }
                }
            }
        }
        cout << min(ans1, ans2);
    }
}