#include<stdio.h>
int main(){
    int n;
    scanf("%d",&n);
    int arr[n];
    int haszero = 0;
    for (int i = 0; i < n; i++);{
        scanf("%d", &arr [i]);
        if(arr[i] == 0)haszero = 1;
    }
    if(!haszero){
        printf("Invalid input");
        return 0;
    }
    int result[n], index = 0;
    for(int i = 0; i<n;i++)
    if(arr[i]!=0) result[index++]=arr[i];
    while (index<n)
    result[index++] = 0;
    for(int i = 0; i< n; i++)
    printf("%d", result[i]);
    return 0;
    
}