Input string was not in a correct format ????

using (SqlConnection con = new SqlConnection(connectionString))
        {
            SqlCommand cmd = new SqlCommand();
            cmd.Connection = con;
            cmd.CommandType = CommandType.StoredProcedure;
            cmd.CommandText = "Loging";
            cmd.Parameters.AddWithValue("@UserName", username);
            cmd.Parameters.AddWithValue("@PassWord", password);
            con.Open();
            int x =Convert.ToInt32(cmd.ExecuteScalar());
            isAuthenticated = x == 1;
            
        }