#include<bitset>
#include<cstdio>
#include<vector>
#include<cassert>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
typedef long long LL;
const int N=103,P=1e9,D=5000;
int n,m,a[N]; LL f[N][N][5000];
int stk[N],tt;
void dfs(int u,int cnt,int r,int S){
    // printf("%d %d %d\n",u,r,S);
    if(!u){
        if(!S&&!cnt&&tt){
            printf("%d ",tt);
            for(int i=1;i<=tt;i++) printf("%d ",stk[i]); puts("");
            exit(0);
        }
        return;
    }
    int t=a[u]%D;
    if(f[u-1][cnt][r]) dfs(u-1,cnt,r,S);
    if(f[u-1][cnt-1][(r-t+D)%D]) stk[++tt]=u,dfs(u-1,cnt-1,(r-t+D)%D,(S+a[u])%P),tt--;
}
void solve(){
    scanf("%d",&n); m=n>>1;
    f[0][0][0]=1;
    for(int i=1;i<=n;i++){
        scanf("%d",&a[i]);
        int t=a[i]%D;
        for(int j=0;j<=m;j++)
            for(int r=0;r<D;r++){
                f[i][j][r]+=f[i-1][j][r];
                f[i][j+1][(r+t)%D]+=f[i-1][j][r];
            }
    }
    dfs(n,m,0,0);
}
int main(){
    int T=1;
    // scanf("%d",&T);
    while(T--) solve();
    return 0;
}