The number of positions

Time Limit: 0.5 second

Memory Limit: 256 megabytes

Description

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.

Input

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

Output

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

Sample Input

Input
3 1 1
Output
2
Input
5 2 3
Output
3

Sample Output

None

Hint

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.

Source

None

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