#include<stdio.h>
int main(){
    int n;
    scanf("%d",&n);
    if(n<0 || n>100){
        printf("-1");
        return 0;
    }
    int arr[n];
    int*p=arr;
    for(int i=0;i<n;i++){
      scanf("%d",(p+i)); 
    }
    int start=0,end=1;
    while (end<n){
        int temp= *(p+start);
        *(pstart)=*(p+end);
        *(p+end)=temp;
        start=start+2;
        end=end+2;
    }
    for(int i=0;i,n;i+=){
        printf("%d",*(p+i));
    }
    return 0;
}