I've tried to figure out the reason for RTE on test case 2 but no way I got stuck. Please, if any coach can submit the solution to tell me which test case gives RTE or if anyone can offer help it will be appreciated.

#include<bits/stdc++.h>
using namespace std;
vector <int> arr[30];
vector <bool> ans;
int main()
{
    freopen("mahdi.in", "r", stdin);
    int t, len, mult, add, n, fir;
    char fir1;

    cin>>t;
    for(int tt=1;tt<=t;tt++)
    {
        ans.erase(ans.begin(), ans.end());
        for(int i=0;i<26;i++)arr[i].erase(arr[i].begin(), arr[i].end());
        cin>>fir1>>len>>mult>>add;
        fir = (fir1 - 97) % 26;
        arr[fir].push_back(0);
        for(int i=1; i<len; i++)
        {
            fir = (fir * mult + i * add) % 26;
            arr[fir].push_back(i);
        }
        cin>>n;
        while(n--)
        {
            cin>>fir1>>len>>mult>>add;
            //if(fir1 < 97)cout<<"dog";
            fir = (fir1 - 97) % 26;
            bool check = 1;
            int pos = -1;
            if(arr[fir].size())
            {
                pos = arr[fir][0];
            }
            if(pos !=-1)
            {
                for(int i=1; i<len; i++)
                {
                    check = 0;
                    fir = (fir * mult + i * add) % 26;
                    int s = 0, e = arr[fir].size(), mid;
                    if(!e) break;
                    while(s < e)
                    {
                        mid = s + (e-s-1)/2;
                        if(pos <= arr[fir][mid])
                        {
                            e = mid;
                        }
                        else if(pos > arr[fir][mid])
                        {
                            s = mid+1;
                        }
                    }
                    if(arr[fir][s] > pos)
                    {
                        pos = arr[fir][s];check=1;
                    }
                    /*for(int j=0; j<arr[fir].size(); j++)
                    {
                        if(arr[fir][j] > pos)
                        {
                            check = 1;
                            pos = arr[fir][j];
                            break;
                        }
                    }*/
                    if(!check)break;
                }
            }
            if(pos == -1 || !check)
                ans.push_back(0);
            else
                ans.push_back(1);
        }
        cout << "Case " << tt << ":\n";
        for(int i=0;i<ans.size();i++)
        {
            if(ans[i]) cout<<"BRAVO\n";
            else cout<<"REPEAT\n";
        }
    }
return 0;
}

Thanks in advance