1 + 3 + 5 + 7 + 9 +...+ 97 + 99 + 100.

1 + 3 + 5 + 7 + 9 +...+ 97 + 99 + 100.

(99 - 1) 은 2 + 1, = 49 + 1, = 50; (99 + 1) × 50 은 2 + 100, = 5000 은 2 + 100, = 2600.