import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] pArray = new int[n];
        for (int i = 0; i < n; i++) {
            pArray[i] = scanner.nextInt();
        }

        int count = 0;
        for (int i = 1; i < n - 1; i++) {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        }

        System.out.println(count);
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] pArray = new int[n];
        for (int i = 0; i < n; i++) {
            pArray[i] = scanner.nextInt();
        }

        int count = 0;
        for (int i = 1; i < n - 1; i++) {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        }

        System.out.println(count);
    }
} Main public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] pArray = new int[n];
        for (int i = 0; i < n; i++) {
            pArray[i] = scanner.nextInt();
        }

        int count = 0;
        for (int i = 1; i < n - 1; i++) {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        }

        System.out.println(count);
    } main {

        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] pArray = new int[n];
        for (int i = 0; i < n; i++) {
            pArray[i] = scanner.nextInt();
        }

        int count = 0;
        for (int i = 1; i < n - 1; i++) {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        }

        System.out.println(count);
    } Scanner scanner = new Scanner(System.in); scanner new Scanner(System.in) int n = scanner.nextInt(); n scanner.nextInt() scanner.nextInt scanner int[] pArray = new int[n]; pArray new int[n] n for (int i = 0; i < n; i++) {
            pArray[i] = scanner.nextInt();
        } int i = 0; int i = 0; i 0 i < n i n i++ i++ i {
            pArray[i] = scanner.nextInt();
        } {
            pArray[i] = scanner.nextInt();
        } pArray[i] = scanner.nextInt() pArray[i] pArray i scanner.nextInt() scanner.nextInt scanner int count = 0; count 0 for (int i = 1; i < n - 1; i++) {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        } int i = 1; int i = 1; i 1 i < n - 1 i n - 1 n 1 i++ i++ i {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        } {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        } if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            } pArray[i] > pArray[i - 1] pArray[i] pArray i pArray[i - 1] pArray i - 1 i 1 {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                } pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1] pArray[i + 1] == pArray[i - 1] pArray[i + 1] pArray i + 1 i 1 pArray[i - 1] pArray i - 1 i 1 pArray[i] <= pArray[i + 1] pArray[i] pArray i pArray[i + 1] pArray i + 1 i 1 {
                    count++;
                } count++ count {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            } if (pArray[i] > pArray[i + 1]) {
                    count++;
                } pArray[i] > pArray[i + 1] pArray[i] pArray i pArray[i + 1] pArray i + 1 i 1 {
                    count++;
                } count++ count System.out.println(count) System.out.println System.out System System.out count String[] args args public class Main {
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] pArray = new int[n];
        for (int i = 0; i < n; i++) {
            pArray[i] = scanner.nextInt();
        }

        int count = 0;
        for (int i = 1; i < n - 1; i++) {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        }

        System.out.println(count);
    }
} public class Main {
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] pArray = new int[n];
        for (int i = 0; i < n; i++) {
            pArray[i] = scanner.nextInt();
        }

        int count = 0;
        for (int i = 1; i < n - 1; i++) {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        }

        System.out.println(count);
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] pArray = new int[n];
        for (int i = 0; i < n; i++) {
            pArray[i] = scanner.nextInt();
        }

        int count = 0;
        for (int i = 1; i < n - 1; i++) {
            if (pArray[i] > pArray[i - 1]) {
                if (pArray[i + 1] == pArray[i - 1]
                        || pArray[i] <= pArray[i + 1]) {
                    count++;
                }
            } else {
                if (pArray[i] > pArray[i + 1]) {
                    count++;
                }
            }
        }

        System.out.println(count);
    }
}