Choosen As Best Answer
For your reference
The solution of 1+2+3 +4+...+n ≥200 is n ≥19.05... .
You should write 1+2+3 +4+...+n ≤ 200 so that the maximin positive integer solution of n is 19.
hi, handsome guy, I got your kindness and thx. The n=19 or n=20 is a number just only for easy to count.