To solve this, I used guess and check.
I started by finding 60²=3600 and 70²=4900. 70² is too much, so I then did 65²=4,225.
After 65², I did 62²=3,844. I knew that was pretty close, so I did 64. 64²=4,096 and 63²=3,969. So, 64² was it.
4,096-4015=81
So, you would need to add 81 to 4015 in order to receive a perfect square, which is 64²(4,096).
