Dev Skill Coin puzzle

//Next Codeforces Round #354 (Div. 2)
#include<bits/stdc++.h>

//#include<cstdio>
//#include<iostream>
//#include<algorithm>
//#include<vector>
//#include<cstring>
//#include<cmath>
//#include<map>

using namespace std;

#define fast ios_base::sync_with_stdio(false)
#define bfast cin.tie(0)
#define outs(x) cout << x << " "
#define outn(x) cout << x << "\n"
#define sf scanf
#define pf printf
#define nl puts("")
#define psb push_back
//#define i64 long long
#define high 30

typedef long long LL;
typedef vector<int>vii;
typedef vector<LL>vll;
typedef vector<char>vc;
typedef map<char, int>mpci;
typedef set<char>sch;

struct bmy
{
    char chboro;
    int bcnt;
};

bmy boro[30];

struct cmy
{
    char chchoto;
    int ccnt;
};

cmy choto[high];

bool cmpboro(bmy a , bmy b)
{
    return a.bcnt > b.bcnt;
}

bool cmpchoto(cmy a , cmy b)
{
    return a.ccnt < b.ccnt;
}

int main()
{
    fast;
    int t , n , q , blen=0, clen=0;
    mpci mpboro, mpchoto, mark;
    string s, ans="";
    cin >> t;
    while(t--)
    {
        mpboro.clear();
        mpchoto.clear();
        mark.clear();

        ans="";

        cin >> n >> q;

        blen=clen=0;

        while(q--)
        {
            cin >> s;

            if(s[1] == '>')
            {
                if(mpboro.count(s[0]) == 0)
                {
                    mpboro[s[0]]++;
                    boro[blen].chboro = s[0];
                    blen++;
                }

                else
                {
                    mpboro[s[0]]++;
                }

                if(mpchoto.count(s[2]) == 0)
                {
                    mpchoto[s[2]]++;
                    choto[clen].chchoto = s[2];
                    clen++;
                }

                else
                {
                    mpchoto[s[2]]++;
                }
            }

            else
            {
                if(mpboro.count(s[2]) == 0)
                {
                    mpboro[s[2]]++;
                    boro[blen].chboro = s[2];
                    blen++;
                }

                else
                {
                    mpboro[s[2]]++;
                }

                if(mpchoto.count(s[0]) == 0)
                {
                    mpchoto[s[0]]++;
                    choto[clen].chchoto = s[0];
                    clen++;
                }

                else
                {
                    mpchoto[s[0]]++;
                }
            }
        }

        for(int i=0; i<blen; i++)
        {
            boro[i].bcnt = mpboro[boro[i].chboro];
        }

        for(int i=0; i<clen; i++)
        {
            choto[i].ccnt = mpchoto[choto[i].chchoto];
        }

        sort(boro, boro+blen, cmpboro);
        sort(choto, choto+clen, cmpchoto);

        for(int i=0; i<blen; i++)
        {
            if(mark.count(boro[i].chboro) == 0)
            {
                ans+=boro[i].chboro;

                mark[boro[i].chboro] = 1;
            }
        }

        for(int i=0; i<clen; i++)
        {
            if(mark.count(choto[i].chchoto) == 0)
            {
                ans+=choto[i].chchoto;

                mark[choto[i].chchoto] = 1;
            }
        }

        //for(int i=0; i<blen; i++) cout << boro[i].chboro << " " << boro[i].bcnt << "\n";
        //for(int i=0; i<clen; i++) cout << choto[i].chchoto << " " << choto[i].ccnt << "\n";

        bool f=true;

        for(int i=0; i<blen; i++)
        {
            if(mpboro[boro[i].chboro] == mpchoto[choto[i].chchoto])
            {
                f=false;
            }

            else
            {
                f=true;
                break;
            }
        }

        for(int i=0; i<clen; i++)
        {
            if(mpchoto[choto[i].chchoto] == mpboro[boro[i].chboro])
            {
                f=false;
            }

            else
            {
                f=true;
                break;
            }
        }

        if(f)
        {
            reverse(ans.begin(), ans.end());
            outn(ans);
        }

        else
        {
            outn("Impossible");
        }
    }

    return 0;
}