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

#define MAX 1000


int isValidInteger(char str[]) {
    int i = 0;

    if (str[0] == '-' || str[0] == '+') {
        i = 1;
    }

    if (str[i] == '\0') return 0; 

    for (; str[i] != '\0'; i++) {
        if (!isdigit(str[i])) return 0;
    }

    return 1;
}

int main() {
    int n;
    char input[100];
    int shipments[MAX];
    
    scanf("%d", &n);
    getchar(); 

    for (int i = 0; i < n; i++) {
        fgets(input, sizeof(input), stdin);
        input[strcspn(input, "\n")] = '\0'; 

        if (!isValidInteger(input)) {
            printf("Invalid input\n");
            return 0;
        }

        int newEntry = atoi(input);
        if (i == 0) {
            shipments[0] = newEntry;