#include <iostream>

using namespace std;

int main()
{
    int n,i,j=0;
    cin>>n;
    int tomb[n+1];
    int b=1,jobb=n;
    for(i=1;i<=n;i++)
    {
        cin>>tomb[i];
    }
   if(tomb[b]>tomb[jobb])
        {
            cout<<b<< " "<<n;
            j=1;
        }
    else
    for(i=1;i<n;i++)
    {
        jobb=n-i;
        b=1;
          while(tomb[b]<=tomb[jobb]&&jobb<=n&&j!=1)
         {
             //cout<<i<<" "<<b<<" "<<jobb<<" "<<endl;
           b++;
           jobb++;
           /*
           if(tomb[b]>tomb[jobb])
           {
            cout<<b<< "bb "<<n;
            j=1;
            break;
           }
           */
         }
         if(tomb[b]>tomb[jobb])
           {
            cout<<b<< " "<<jobb;
            j=1;
            break;
           }

    }
    if(j==0)
    cout<<-1;
    return 0;
}