#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a, b, pos, cnt = 0;
  cin >> n >> a >> b;
  for (int pos = 1; pos <= n; pos++) {
    if (n - pos <= b && pos - 1 >= a) cnt++;
  }
  cout << cnt;
  return 0;
}
