#include <bits/stdc++.h>
using namespace std;

//repetition
#define FOR(i,a,b) for(ll i=(a);i<(b);++i)
#define rep(i, n) for(ll i = 0; i < (ll)(n); i++)

//container util
#define all(x) (x).begin(),(x).end()

//typedef
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
typedef vector<ll> VLL;
typedef vector<VLL> VVLL;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<ll, ll> PLL;

//const value
//const ll MOD = 1e9 + 7;
//const int dx[] = {0,1,0,-1};//{0,0,1,1,1,-1,-1,-1};
//const int dy[] = {1,0,-1,0};//{1,-1,0,1,-1,0,1,-1};

//conversion
inline int toInt(string s) {int v; istringstream sin(s);sin>>v;return v;}
inline ll toLL(string s) {ll v; istringstream sin(s);sin>>v;return v;}
template<class T> inline string toString(T x) {ostringstream sout;sout<<x;return sout.str();}


void rot45(PII & p){
  int x = p.first - p.second;
  int y = p.first + p.second;
  p.first = x;
  p.second = y;
}

int main(){
  ios::sync_with_stdio(false);
  cin.tie(0);
  ll x, y,d;
  cin >> x >> y >> d;
  if(d == 0){
    cout << 1 << endl;
    return 0;
  }
  PII xend, yend;
  if(d <= x) {
    xend = PII(d,0);
  } else{
    if( d - x <= y) xend = PII(x,d-x);
    else{
      cout << 0 << endl;
      return 0;
    }
  }

  if(d <= y) {
    yend = PII(0,d);
  } else{
    if( d - y <= x) xend = PII(d-x,y);
    else{
      cout << 0 << endl;
      return 0;
    }
  }

  // rot45(xend);
  // rot45(yend);
  // cout << "xend = ( " << xend.first << " , " << xend.second << " )" << endl;
  // cout << "yend = ( " << yend.first << " , " << yend.second << " )" << endl;

  cout << abs(xend.first - yend.first) + 1 << endl;


  return 0;
}