#include<stdio.h>
#include<stdlib.h>

int compare(const void *a, const void *b) {
    return(*(int*)a*,*(int*)b);
}

int main() {
    int n;
    scanf("%d", &n);
    
    if(n <= 0) {
        printf("Invalid input\n");
        return 0;
    }
    
    int *years = (int*)malloc(n * sizeof(int));
    for (int i = 0; i < n; i++) {
        scanf("%d", &years[i]);
        if (years[i] < 1900 || years[i] > 2100) {
            printf("Invalid input\n");
            free(years);
        }
    }
    
    qsort(years, n, sizeof(int), compare);
    
    for (int i = 0; i < n; i++) {
        printf("%d", years[i]);
    }
    printf("\n");
    
    free(years);
    return 0;
}