how to avoid data repetition while insert in laravel

i have data like company has branch in multiple city and each city has company three different offices office1, office2 and office3

Data is like below,

• company1

  • city1
    • Address of office 1, Address of office 2, Address of office 3
  • city2
    • Address of office 1, Address of office 2, Address of office 3
  • city3
    • Address of office 1, Address of office 2, Address of office 3

• company2

  • city1
    • Address of office 1, Address of office 2, Address of office 3
  • city2
    • Address of office 1, Address of office 2, Address of office 3
  • city3
    • Address of office 1, Address of office 2, Address of office 3

So i need to validate that once company1 address store for city1 then it should not be stored again database, as well if address of office 1 stored for city1 then it will not be stored again. I used laravel 5.3 version.

via user3649115