C++ multi user login system (non functional for now)

#include <iostream>
#include <vector>

using namespace std;

int
main ()
{
  vector < string > accinfo =
  {
  "admin admin"};
  string hpass = "";
  string hem = "";
  string facc = "";
  string phem = "";
  string phpass = "";
  string len = "";
  int a = 0;
  int b = 0;
  int lloop = 0;

  a = 1;
  while (a == 1)
    {
      a = 2;
      cout << "Welcome to the website!\n\n";
      cout << "Would you like to register or login?\n1) register\n2) login\n";
      cin >> b;

      if (b == 1)
    {
      cout << "Thank you for regsitering with us!\n\n";
      cout << "Please enter your email:\n";
      cin >> hem;
      cout << "Please enter a password:\n";
      cin >> hpass;
      if (hem != "" && hpass != "")
        {
          cout << "Registration complete!\n\n";
          facc = hem + " " + hpass;
          accinfo.push_back (facc);
          a = 1;

        }
      else
        {
          cout << "Invalid entry for: password/email\n";
          a = 1;
        }

    }
      else if (b == 2)
    {
      cout << "Login:\n\n";
      cout << "enter email:\n";
      cin >> phem;
      cout << "enter password:\n";
      cin >> phpass;
      len = phem + phpass;
      for (int i = 0; i < accinfo.size (); i++)
        {

          if (len == accinfo[i])
        {
          lloop = 1;
          while (lloop == 1)
            {
              lloop = 0;
              cout << "Succesful login!\n";
            }
        }
          else if (i < accinfo.size() && len != accinfo[i])
        {
          lloop = 1;
        }
          else if (i == accinfo.size() && len != accinfo[i])
        {
          cout << "Login failed";
          a == 1;
        }
          else if (i == accinfo.size() && len == accinfo[i])
        {
          cout << "Login Succesful";
        }


        }
    }

    }



}