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#include<iostream>
#include<vector>
using namespace std;
int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    long long n;
    cin >> n;
    vector<long long>v(n);
    for(auto&i:v){cin>>i;}
    long long cg=0,cd=0;
    long long p=v[0];
    for(long long i=1;i<n;i++){
        if(i%2){
            if(v[i]<=p){cg++;p=1000000000;}
            else{p=v[i];}
        }
        else{
            if(v[i]>=p){cg++;p=-1000000000;}
            else{p=v[i];}
        }
    }
    p=v[0];
    for(long long i=1;i<n;i++){
        if(i%2==0){
            if(v[i]<=p){cd++;p=1000000000;}
            else{p=v[i];}
        }
        else{
            if(v[i]>=p){cd++;p=-1000000000;}
            else{p=v[i];}
        }
    }
    cout<<min(cd,cg)<<endl;
}