|Codeforces Round #273 (Div. 2)|
There are r red and g green blocks for construction of the red-green tower. Red-green tower can be built following next rules:
Let h be the maximum possible number of levels of red-green tower, that can be built out of r red and g green blocks meeting the rules above. The task is to determine how many different red-green towers having h levels can be built out of the available blocks.
Two red-green towers are considered different if there exists some level, that consists of red blocks in the one tower and consists of green blocks in the other tower.
You are to write a program that will find the number of different red-green towers of height h modulo 109 + 7.
The only line of input contains two integers r and g, separated by a single space — the number of available red and green blocks respectively (0 ≤ r, g ≤ 2·105, r + g ≥ 1).
Output the only integer — the number of different possible red-green towers of height h modulo 109 + 7.
The image in the problem statement shows all possible red-green towers for the first sample.