#include <algorithm>
#include <iostream>
using namespace std;

int main() {
  int X, Y, Z;
  cin >> X >> Y >> Z;
  --X, Y += Z + 1;
  int ans = 0;
  for (int i = 0; i <= Z; ++i) {
    ++X, --Y;
    ans = max(min(X, Y), ans);
  }
  cout << ans << endl;
}