#include <bits/stdc++.h>
int main() {
  int n, a, b, i, j, k = 1;
  scanf("%d%d%d", &n, &a, &b);
  for (i = a; i < n; i++)
    for (j = 1; j <= b; j++)
      if (n - i - j == 1) {
        k = k++;
      }
  printf("%d", k);
  return (0);
}
