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#include <bits/stdc++.h>

using namespace std;
#define PB push_back
#define LL long long
#define int LL
#define FOR(i,a,b) for (int i = (a); i <= (b); i++)
#define FORD(i,a,b) for (int i = (a); i >= (b); i--)
#define REP(i,n) FOR(i,0,(int)(n)-1)
#define st first
#define nd second
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((int)(x).size())
#define VI vector<int>
#define PII pair<int,int>
#define LD long double


template<class T> ostream &operator<<(ostream &os, vector<T> V){
    os<<"[";for(auto vv:V)os<<vv<<",";return os<<"]";
}

template<class L, class R> ostream &operator<<(ostream &os, pair<L,R> P) {
    return os << "(" << P.st << "," << P.nd << ")";
}


template<class C> void mini(C& a4, C b4) { a4 = min(a4, b4); }
template<class C> void maxi(C& a4, C b4) { a4 = max(a4, b4); }

template<class TH> void _dbg(const char *sdbg, TH h){cerr<<sdbg<<"="<<h<<"\n";}
template<class TH, class... TA> void _dbg(const char *sdbg, TH h, TA... a) {
    while(*sdbg!=',')cerr<<*sdbg++;cerr<<"="<<h<<","; _dbg(sdbg+1, a...);
}


#ifdef LOCAL
#define debug(...) _dbg(#__VA_ARGS__, __VA_ARGS__)
#else
#define debug(...) (__VA_ARGS__)
#define cerr if(0)cout
#endif


int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout << fixed << setprecision(11);
    cerr << fixed << setprecision(6);
    int n;
    cin >> n;
    VI a(n);
    REP(i, n){
        cin >> a[i];
    }
    vector<vector<bool>> options(2, vector<bool>(n - 1));
    REP(d, 2){
        for(int i = d; i < n - 1; i += 2){
            options[d][i] = true;
        }
    }
    int result = INT_MAX;
    REP(d, 2){
        int current = 0;
        REP(i, n - 1){
            int v1 = a[i];
            int v2 = a[i + 1];
            if(v1 == v2 || (v1 < v2) != options[d][i]){
                current++;
                i++;
            }
        }
        mini(result, current);
    }
    cout << result << "\n";
}