# include <stdio.h>
long n, v[500000], a[500000], i, k;

int main()
{
freopen("reguli.in","r",stdin);
freopen("reguli.out","w",stdout);
scanf("%ld",&n);
for (i=1;i<=n;i++)
   {
   scanf("%ld",&v[i]);
   if (i>=2)
     a[i-1]=v[i]-v[i-1];
   }
k=1;
for (i=2;i<n;i++)
   if (a[i]!=a[i-k])
     k=i;
printf("%ld\n",k);
for (i=1;i<=k;i++)
   printf("%ld ",a[i]);
printf("\n");
return 0;
}