#include <stdio.h>
#include <string.h>
#define NMAX 500500

long long X[NMAX], A[NMAX];
int N, K;

int main()
{
        int ok, i, poz, k;

        freopen("reguli.in", "r", stdin);
        scanf("%d", &N);

        for (i = 1; i <= N; i++)
            scanf("%lld", &X[i]);

        for (i = 1; i < N; i++) A[i] = X[i+1]-X[i];

        poz = 1;
        for (i = 2; i < N; i++)
            if (A[i] == A[poz]) poz++;
            else
                if (A[i] == A[1]) poz = 2;
                else poz = 1;

        freopen("reguli.out", "w", stdout);
        printf("%d\n", N-poz);
        for (i = 1; i <= N-poz; i++) printf("%lld\n", A[i]);
        
        return 0;
        
}