The number of positions
说明
A. The number of positions
time limit per test
0.5 secondmemory limit per test
256 megabytesinput
standard inputoutput
standard outputPetr 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.
Examples
Input
3 1 1
Output
2
Input
5 2 3
Output
3
Note
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.
样例
