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#include <bits/stdc++.h>

using namespace std;

const int N = 5e3+1;

int a[N], dp[N][2], n;

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    cin>>n;
    for (int i=1; i<=n; ++i) cin>>a[i];

    int ans=1e9+2137+69+420;
    // start increasing
    memset(dp, 0, sizeof(dp));
    dp[1][1]=1;

    for (int i=2; i<=n; ++i) {
        dp[i][0]=dp[i-1][1];
        if (i&1) {
            if (a[i-1] > a[i]) dp[i][0]=min(dp[i][0], dp[i-1][0]);
            dp[i][1]=min(dp[i-1][0], dp[i-1][1])+1;
        } else {
            if (a[i-1] < a[i]) dp[i][0]=min(dp[i][0], dp[i-1][0]);
            dp[i][1]=min(dp[i-1][0], dp[i-1][1])+1;
        }
    }
    ans=min({ans, dp[n][0], dp[n][1]});

    // start decreasing
    memset(dp, 0, sizeof(dp));
    dp[1][1]=1;

    for (int i=2; i<=n; ++i) {
        dp[i][0]=dp[i-1][1];
        if (i&1) {
            if (a[i-1] < a[i]) dp[i][0]=min(dp[i][0], dp[i-1][0]);
            dp[i][1]=min(dp[i-1][0], dp[i-1][1])+1;
        } else {
            if (a[i-1] > a[i]) dp[i][0]=min(dp[i][0], dp[i-1][0]);
            dp[i][1]=min(dp[i-1][0], dp[i-1][1])+1;
        }
    }

    ans=min({ans, dp[n][0], dp[n][1]});

    cout<<ans<<"\n";
}