What is the single digit of 2 to the power of 1998 plus 3 to the power of 1998

What is the single digit of 2 to the power of 1998 plus 3 to the power of 1998

Two n-th power results: 24 8 16 32, indicating that the end number is a cycle of 4 numbers
Three n-th power results: 39 27 71 213, indicating that the end number is also a cycle of four numbers
1998 / 4 = 499 and more than 2, indicating that the end result of the 1998 power of 2 is 4, and the end result of the 1998 power of 3 is 9. After adding 4 + 9 = 13, the end number is 3