#include <iostream>
#include <map>
#include <set>
#include <vector>
#include <queue>
#include <cstdio>

#define DEBU

#ifdef DEBUG
	#define DBG if (1)
#else
	#define DBG if (0)
#endif

#define PA(arr, n) DBG for (int i = 0; i < n; i++) printf("%d%c", arr[i], "\n "[i < n - 1])
#define PD(n) DBG printf("%d\n", d); 
#define PDBL(n) DBG printf("%lf\n", d);

using namespace std;

int main () {

	int n;
	while(scanf("%d", &n) == 1){

	vector<int> arr(n, 0);
	for (int i = 0; i < n; i++) {
		scanf("%d", &arr[i]);	
	}
	if(n == 1) {
		printf("1\n");
		return 0;	
	}

	int diff = 0;
	int i = arr.size()-1;
	diff = arr[arr.size()-1]-arr[arr.size()-2];
	while(arr[i]-arr[i-1] == diff && i > 0)
		i--;  
	
	printf("%d\n",i+1);
	PA(arr, n);
	}
	return 0;

}