#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int main() {
  ll l, r, m; cin >> l >> r >> m;
  if (l + m - 1 <= r) cout << m << endl;
  else cout << m - (l + m - 1 - r) << endl;
  return 0;
}