#include<stdio.h>

int main(){
    int n;
    scanf("%d",&n);
    if(n<0){
        printf("-1");
        return 0;
    }
    int arr[n];
    for(int i=0; i<n; i +=2;){
        scanf("%d",&arr[i]);
        int temp = arr[i];
        arr[i] = arr[i+1];
        arr[i+1] = temp;
        printf("%d ",arr[i]);
    }
    return 0;
}