#include <stdio.h>

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