#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( d > max(x,y) ) puts("0");
  else cout << min(min(x+1,d+1),min(y+1,d+1)) << endl;
  return 0;
}