#include<stdio.h>
int main(){
    int n;
    scanf("%d",&n);
    if(n<=0 ){
        printf("Invalid input");
        return 0;
    }
    int arr[n];
    for(int i=0;i<n;i++){
        scanf("%d",&arr[i]);
    }
    int f=1;
    if(arr[0]==-1){
        printf("Invalid input");
        return 0;
    }
    for(int i=0;i<n;i++){
        if(arr[i]==-1)
            continue;
        if(i!=0 && arr[(i-1)/2]==-1)
            continue;
            
            int left=2*i+1;
            int right=2*i+2;
            
            int isleaf=1;
            if(left<n && arr[left]!=-1)
                isleaf=0;
            if(right<n && arr[right]!=-1)
                isleaf=0;
                
            if(isleaf){
                if(!f)printf(" ");
            
                printf("%d ",arr[i]);
                f=0;
        
    }
    return 0;
}