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#include <bits/stdc++.h>

using namespace std;

#define ll long long

#define rng(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,b) rng(i,0,b)

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<vvi> vvvi;

typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<vvl> vvvl;

typedef pair<int,int> ii;

template<class t> using vc=vector<t>;
template<class t> using vvc=vc<vc<t>>;

const int MOD = 998244353;

ll read(){
    ll i;
    cin>>i;
    return i;
}

vi readvi(int n,int off=0,int shift=0){
    vi v(n+shift);
    rep(i,shift)v[i]=0;
    rep(i,n)v[i+shift]=read()+off;
    return v;
}

void YesNo(bool condition, bool do_exit=true) {
    if (condition)
        cout << "Yes" << endl;
    else
        cout << "No" << endl;
    if (do_exit)
        exit(0);
}

int solve (int n, vi & a) {
    int res = 0;
    int cnt = 0;
    rep(i, n-1) {
        if (i % 2) {
            if (a[i] <= a[i+1]) // bad
                ++cnt;

            if (a[i] > a[i+1] or i == n-2) {
                res += (cnt+1)/2;
                cnt = 0;
            }
        } else {
            if (a[i] >= a[i+1]) // bad
                ++cnt;

            if (a[i] < a[i+1] or i == n-2) {
                res += (cnt+1)/2;
                cnt = 0;
            }
        }

    }
    return res;
}

int main(void ) {
    ios::sync_with_stdio(false);
    cin.tie(NULL);

    int n;
    cin >> n;

    vi a = readvi(n);

    int res = solve(n,a);
    rep(i,n)
        a[i] = -a[i];
    res = min(res, solve(n,a));

    cout << res << endl;

    return 0;
}