【题目描述】 一个人站在一个总人数为n队列里，他前面有不少于a个人，后面有不多于b个人。求他有多少种可能的不同位置。 【输入格式】 输入n,a,b (0<=a,b,n<=100) 【输出格式】 一个数，即这个人有多少种可能的不同位置
Translated by @隐鬼在侧
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.
The only line contains three integers $ n $ , $ a $ and $ b $ ( $ 0<=a,b<n<=100 $ ).输出格式：
Print the single number — the number of the sought positions.
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.