Petr stands in line of n people, but he doesn't know exactly which position he occupies. He can say that there are no less than a people standing in front of him and no more than b people standing behind him. Find the number of different positions Petr can occupy.

输入描述:

The only line contains three integers n, a and b (0 ≤ a, b n ≤ 100).

输出描述:

Print the single number — the number of the sought positions.

备注:

The possible positions in the first sample are: 2 and 3 (if we number the positions starting with 1).In the second sample they are 3, 4 and 5.