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#include <stdio.h>
#include <stdlib.h>

#define M 1000001

#define MIN(X, Y) (((X) < (Y)) ? (X) : (Y))

int check(int *buff, int n, int up) {
    int i,p;
    int ret = 0;

    p = up ? -M : M;

    for (i=0; i<=n; ++i) {
        if (up) {
            if (buff[i] > p) {
                p = buff[i];
            } else {
                ret++;
                p = M;
            }
        } else {
            if (buff[i] < p) {
                p = buff[i];
            } else {
                ret++;
                p = -M;
            }
        }
        up = !up;
    }
    return ret;
}

int main() {
    int n, *buff,i,a,b;
    scanf("%d\n", &n);
    buff = (int *)malloc(n*sizeof(*buff));

    for (i=0; i<n; ++i)
        scanf("%d", buff+i);

    a = check(buff,n,1);
    b = check(buff,n,0);   

    printf("%d\n", MIN(a,b));


    free(buff);
    return 0;
}