1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
#include <bits/stdc++.h>

#define INF 2147483647
#define LINF 9223372036854775807
#define NINF -2147483648
#define NLINF -9223372036854775808
#define M 1000000007
#define M1 998244353
#define A 26
#define K 31
#define P 2137

using namespace std;
using db=double;
using dbl=long double;
using ll=long long;
using pi=pair<int,int>;
using pl=pair<ll,ll>;
using vi=vector<int>;
using vl=vector<ll>;
using gr=vector<vector<int> >;
using grl=vector<vector<ll> >;


#define fp(x, a, b) for (int (x) = (a); (x) < (b); (x)++)
#define f(x, n) for (int (x) = 0; (x) < (n); (x)++)
#define fnp(x, a, b) for (int (x) = (b) - 1; (x) >= (a); (x)--)
#define fn(x, n) for (int (x) = (n - 1); (x) >= 0; (x)--)
#define sgn(x) (x) > 0 ? 1 : (x) == 0 ? 0 : -1
#define gcd(a, b) __gcd((a), (b))
#define lcm(a, b) (a) * (b) / gcd((a), (b))
#define x first
#define y second
#define mp make_pair
#define pb push_back
#define s(x) x.size()
#define all(x) x.begin(), x.end()
#define ans(x) cout<<(x)<<"\n"
#define yes cout<<"YES\n";
#define no cout<<"NO\n";
#define fl cout.flush()
#define debarr(x, n) f(i, (n)){cout<<(x)[i]<<" ";}cout<<"\n"
#define debgr(x, n) f(i, (n)){f(j, s((x)[i])){cout<<(x)[i][j]<<" ";}cout<<"\n";}


mt19937 rnd(chrono::high_resolution_clock::now().time_since_epoch().count());

void input();
void compute();

int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    //cin >> T;
    while(T--)
    {
        input();
        compute();
    }
    return 0;
}

#define N 50001

int n;
int a[N];
int c;
int w;

void input()
{
	cin >> n;
	f(i, n) {
		cin >> a[i];
	}
}

void compute()
{
	w = 0;
	c = 0;
	f(i, n - 1) {
		if(i & 1) {
			if(a[i] <= a[i + 1]) {
				c++;
				i++;
			}
		} else {
			if(a[i] >= a[i + 1]) {
				c++;
				i++;
			}
		}
	}
	f(i, n - 1) {
		if(i & 1) {
			if(a[i] >= a[i + 1]) {
				w++;
				i++;
			}
		} else {
			if(a[i] <= a[i + 1]) {
				w++;
				i++;
			}
		}
	}
	w = min(w, c);
	ans(w);
}