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.

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.
# -*- coding: utf-8 -*-
#
# 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.
# 
# n a b
# 3 1 1 -> 2(1番目か2番目にいるはず。0-index)
# 5 2 3 -> 3(2番目か3番目か4番目にいるはず。0-index)

n, a, b = map(int, raw_input().split())
res = 0
for pos in xrange(n):
  front = pos
  back = n - pos - 1
  if front >= a and back <= b:
    res += 1
print res
