#include<bits/stdc++.h>

#define REP(i,s,n) for(int i=s;i<n;i++)
#define rep(i,n) REP(i,0,n)

using namespace std;

typedef long long ll;

int main(){
  ll x,y,d;
  cin >> x >> y >> d;
  if( x + y < d ) puts("0");
  else {
    ll sp[2];
    if( d >= y ) sp[0] = d - y;
    else         sp[0] = 0;
    sp[1] = min(d,x);
    cout << sp[1] - sp[0] + 1 << endl;
  }
  return 0;
}