#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
int checker(int,int*);
int main()
{
    int n;
    scanf("%d",&n);
    int *p = malloc((2*n+1)*sizeof(int));
    for (int i = 0; i < 2*n+1; i++)
        scanf("%d", &p[i]);
    int a = checker(2*n+1,p);
    if (a == 0)
        printf("it is!");
    else
        printf("Not!");
    return 0;
}
int checker(int a, int* p)
{
    if (a == 0)
        return 0;
    if (p[a]+ p[0] != p[a-1] + p[1])
        return 5000;
    return checker(a-1,p+1);
}