#include <cstdio>
#include <algorithm>

using namespace std;

int main(void) {
  long long x, y, d;
  scanf("%lld%lld%lld", &x, &y, &d);
  long long res = d+1;
  res -= max(0ll, d-x);
  res -= max(0ll, d-y);
  printf("%lld\n", max(0ll, res));
  return 0;
}