参考答案：

#include<iostream>

using namespace std;

int main()
{
    int n, a, b;

    cin >> n >> a >> b;
    if (a + b >= n) cout << n - a;
    else cout << b + 1;

    return 0;
}

Python:

n, h, t = map(int, input().split())

p_min = max(h + 1, n - t)
ans = n - p_min + 1

if ans < 0:
    ans = 0

print(ans)