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