Hi, I suggest you to do it using vector but if you want to use array then please have a look on the below approach.

#include <iostream>
#define LIMIT 100

 

  using namespace std;
    int main()
    {
            string first_name[LIMIT];
            string last_name[LIMIT];
            string str1;
            string str2;
            int j = 0;
            char sentinelCharater = 'n';
            char sentinelInput;
                    cout << "Enter 'y' to continue else 'n' to stop taking inputs : ";
            cin >> sentinelInput;
                while(sentinelInput != sentinelCharater) {
                    cin >> str1 >> str2;
                    first_name[j] = str1;
                    last_name[j] = str2;
                    j++;
                    cout << "Enter 'y' to continue else 'n' to stop taking inputs : ";
                    cin >> sentinelInput;
            }
            cout << "\n\nResults" << endl;
            for (int i = 0; i < j; i++)
                    cout << first_name[i] << "." << last_name[i] << "@" << "stallion.edu" << endl;
            return 0;
    }

Thank you, so much !