#include <bits/stdc++.h>
#define dbg(i,j) cout<<"I am "<<i<<" = "<<endl<<j<<endl;
#define dbr(name,a) cout<<name<<endl;for(auto x:a)cout<<x<<" ";cout<<endl;
#define DBR(name,a) cout<<name<<endl;for(auto x:a){ for(auto y:x)cout<<y<<" ";cout<<endl;}
#define dbmp(name,a) cout<<name<<endl;for(auto x:a){ cout<<x.first<<"\t"<<x.second<<endl;}
#define dbp(name,a) cout<<name<<endl;cout<<a.first<<"\t"<<a.second<<endl;
#define boost ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;

typedef long long int big;

typedef  long double fig;

big val(char c)
{
    if (c >= '0' && c <= '9')
        return (big)c - '0';
    else
        return (big)c - 'A' + 10;
}




big toDeci(string str, big base)
{
    big len = str.size();
    big power = 1; // Initialize power of base
    big num = 0;  // Initialize result
    big i;
 //     dbg("base",base);
    // Decimal equivalent is str[len-1]*1 +
    // str[len-1]*base + str[len-1]*(base^2) + ...
    for (i = len - 1; i >= 0; i--)
    {
        // A digit in input number must be
        // less than number's base
        if (val(str[i]) >= base)
        {
           printf("Invalid Number");
           return -1;
        }

        num += val(str[i]) * power;
        power = power * base;
    }

    return num;
}




int main(){
    big t;
    cin>>t;
    while(t--){
        big n;
        cin>>n;
        vector<vector<big>> bag;
        for(big i=0;i<n;i++){
            big a;
            string s;
            cin>>a;
            cin>>s;
            vector<big> temp;
            if(a==-1){

                vector<big> arr;
                for(auto x:s){
                    if(x>=48 && x<=57){
                        arr.push_back(x-48);
                    }
                    else{
                        arr.push_back(10+(x-'A'));
                    }
                }
                big base=*max_element(arr.begin(),arr.end())+1;
                if(base==1){
                    base=2;
                }

                for(big z=base;z<=36;z++){
                    temp.push_back(toDeci(s,z));
                }
            }
            else{
                temp.push_back(toDeci(s,a));
            }
            bag.push_back(temp);
        }
    //  DBR("BAG",bag);
        big ans=-1;
        big start[n]={0};
        for(big j=0;j<bag[0].size();j++){
            big check=bag[0][j];
        //  dbg("check",check);
            big flag=0;
            for(big z=1;z<n;z++){
                for(big c=start[z];c<bag[z].size();c++){
        //          dbg("checking with",bag[z][c]);
                    if((check==bag[z][c])){
                        flag++;
                        start[z]=c;
                        break;
                    }
                    else if(check<bag[z][c]){
                        start[z]=c;
                        break;
                    }
                }
            }
            if(flag==n-1){
                ans=bag[0][j];
                break;
            }
        }
        cout<<ans<<endl;
    }
    return 0;
}