#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
//ifstream f("data.in");
struct c{
	int v;
	int p;
};
c vec[400005];
int n;
bool cmp(c a,c b)
{
	if(a.v>=b.v)
		return 0;
	return 1;
}
int main()
{
	int i,j;
	cin>>n;
	for(i=1;i<=n;i++)
	{
		cin>>vec[i].v;
		vec[i].p=i;
		//p[i]=v[i];
		//cout<<v[i]<<" ";
	}
	sort(vec+1,vec+1+n,cmp);
	//for(i=1;i<=n;i++)
		//cout<<vec[i].v<<" ";
	for(i=1;i<n;i++)
	{
		//if(vec[i].v==n)
		//{
			//cout<<1<<"\n"<<i<<"\n";
			//return 0;
		//}
		if(vec[i].v<n)
			for(j=i+1;j<=n;j++)
			{
				//if(vec[j].v==n)
				//{
					//cout<<1<<"\n"<<i<<"\n";
					//return 0;
				//}
				if(vec[j].v+vec[i].v==n)
				{
					if(vec[i].p<vec[j].p)
						cout<<2<<"\n"<<vec[i].p<<" "<<vec[j].p<<"\n";
					else
						cout<<2<<"\n"<<vec[j].p<<" "<<vec[i].p<<"\n";
					return 0;
				}
			}
		else 
			return 0;
	}

}