solution a

#include<bits/stdc++.h>
using namespace std;

int main()
{
    int test;
    int n;
    int arr[100005];
    cin>>test;
    while(test--){
        cin>>n;
        for(int i = 0; i < n; i++){
            cin>>arr[i];
        }
        sort(arr,arr+n);
        int b = arr[n-2];
        cout<<min(n-2,b-1)<<endl;
    }
    return 0;
}