when submitted under c++14/c++17 it was giving runtime error but accepted by c++20

#include <bits/stdc++.h>
#define int long long
#define mod 1000000007
using namespace std;
int fast_pow (int b , int p)
{
    if(p==0)
        return 1;
    return p%2 ?  (b*(fast_pow((b*b)%mod,p/2)%mod))%mod : fast_pow((b*b)%mod,p/2)%mod ;
}


int32_t main()
{
       ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    #ifndef ONLINE_JUDGE
    freopen("input.txt","r",stdin);
    freopen("output.txt","w",stdout);
    freopen("error.txt","w",stderr);

    #endif
    int t;
    cin>>t;
    while(t--){
        
        
        int n,m;
        cin>>n>>m;
        vector<int> v(n);
        for(int &a:v) cin>>a;
        string s;
        cin>>s;
        int i=0,j=n-1;
        for(auto val:s){
            if(i>=j) break;
            if(val=='L') i++;
            else j--;
        }
        int p=v[i];
        vector<int> ans;
        p%=m;
        ans.push_back(p);
        for(int k=s.size()-2;k>=0;k--){
            if(s[k]=='L'){
                i--;
                p*=v[i];
                p%=m;


            }
            else{
                j++;
                p*=v[j];
                p%=m;

            }
            ans.push_back(p);

        }
        std::reverse(ans.begin(), ans.end());
        for(auto val:ans) cout<<val<<" ";
        cout<<endl;


    }












}