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#include <bits/stdc++.h>
using namespace std;
constexpr int maxN = 5e4+7;

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

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

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    cin>>n;
    for(int i=1;i<=n;i++)
        cin>>a[i];
    cout<<min(solve(0), solve(1))<<"\n";
}

/*

5
4 1 3 3 1

4
-1000000 -1000000 -1000000 -1000000



*/