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

typedef long long LL;
typedef long double LD;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;

#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()

template<typename _T> inline void _DBG(const char *s, _T x) { cerr << s << " = " << x << "\n"; }
template<typename _T, typename... args> void _DBG(const char *s, _T x, args... a) { while(*s != ',') cerr << *s++; cerr << " = " << x << ','; _DBG(s + 1, a...); }

#ifdef LOCAL
#define _upgrade ios_base::sync_with_stdio(0);
#define DBG(...) _DBG(#__VA_ARGS__, __VA_ARGS__)
#else
#define _upgrade ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define DBG(...) (__VA_ARGS__)
#define cerr if(0) cout
#endif

// ********************** CODE ********************** //

const int N = 5e4 + 7;
const int INF = 1e9;

int n, A[N];

int main()
{
    _upgrade
    
    cin >> n;
    for (int i = 0; i < n; i++)
        cin >> A[i];

    int first_way = 0, second_way = 0;

    int last = -INF;
    for (int i = 0; i < n; i++)
    {
        if (i % 2 == 0)
        {
            if (!(last < A[i]))
            {
                first_way++;
                last = INF;
            }
            else
                last = A[i];
        }
        else
        {
            if (!(last > A[i]))
            {
                first_way++;
                last = -INF;
            }
            else
                last = A[i];
        }
    }

    last = INF;
    for (int i = 0; i < n; i++)
    {
        if (i % 2 == 0)
        {
            if (!(last > A[i]))
            {
                second_way++;
                last = -INF;
            }
            else
                last = A[i];
        }
        else
        {
            if (!(last < A[i]))
            {
                second_way++;
                last = INF;
            }
            else
                last = A[i];
        }
    }

    cout << min(first_way, second_way) << "\n";

    return 0;
}