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#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair <int, int> pii;
#define se second
#define fi first

const int N = 5e4;
const int INF = 1e9;

int n, res1, res2;
int a[N + 5], b[N + 5];

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    cin >> n;
    for(int i=0; i<n; i++){
        cin >> a[i];
        b[i] = a[i];
    }
    for(int i=1; i<n; i++){
        if(i % 2){
            if(a[i] >= a[i - 1]){
                a[i] = -INF;
                res1 ++;
            }
            if(b[i] <= b[i - 1]){
                b[i] = INF;
                res2 ++;
            }
        }else{
            if(a[i] <= a[i - 1]){
                a[i] = INF;
                res1 ++;
            }
            if(b[i] >= b[i - 1]){
                b[i] = -INF;
                res2 ++;
            }
        }
    }
    cout << min(res1, res2) << "\n";

    return 0;
}