#include<stdio.h>
long long a[500003];
long long b[500003];
int n;
int contor;
int P;

int main()
{
    freopen("reguli.in","r",stdin);
    freopen("reguli.out","w",stdout);

    scanf("%d",&n);
    for(int i = 1; i <= n; i++)
     scanf("%lld",&a[i]);
    for(int i = 2; i <= n; i++)
     b[i] = a[i] - a[i - 1];
    contor = 2;
    P = 2;
    for(int i = 3; i <= n; i++)
         {
             if (b[i] == b[contor])
               {
                   if (contor == P) contor = 2;
                            else contor++;

               }
               else
                {
                    P = i;
                    contor = 2;
                }

         }
     printf("%ld\n", P - 1);
     for(int i = 2; i <= P; i++)
      printf("%lld\n", b[i]);



}