#include<stdio.h>
#include<stdlib.h>
int main() {
    if (scanf("%d", &n) !=1 || n < 1 || n > 100) {
        printf("Invalid");
        return 0;
    }
    int *a = (int *)malloc(n * sizeof(int));
    if (!a) {
        printf("Invalid");
        return 0;
        }
        for (int i = 0; i < n; i++) {
            if (scanf("%d", &a[i]) != 1) {
                printf("Invalid");
                free(a);
                return 0;
            }
        }
        for (int i = 0; i < n -1; i += 2) {
            int temp = a[i];
            a[i] = a[i + 1];
            a[i + 1] = temp;
        }
        for (int i = 0; i < n; i++)
        printf("%d ", a[i]);
        free(a);
        return 0;
}