#include<iostream>
#include<string>
#include<map>
#include<vector>
#include<list>
#include<queue>
#include<stack>
#include<deque>
#include<set>
#include<bitset>
#include<functional>
#include<utility>
#include<iterator>
#include<algorithm>
#include<sstream>
#include<fstream>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<ctime>
#include<cstring>
#include<iomanip>
using namespace std;
#define len(val) static_cast<int>(val.size())
#define rep(i, N) for(int i=0; i<N; i++)
typedef long long ll;
typedef pair<int, int> P;

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);

    int x, y, d;
    cin >> x >> y >> d;
    int res;
    if(x > d){
        if(y > d){
            res =  (d+1);
        }else if(y == d){
            res = (d-x+y+1);
        }else{
            res = (d-x+y+2);
        }
    }else if(x == d){
        if(y > d){
            res = (d+1);
        }else if(y == d){
            res = (d+1);
        }else{
            res = (y+1);
        }
    }else{
        if(y > d){
            res = (x+1);
        }else if(y == d){
            res = (d-y+x+1);
        }else{
            res = (x+y-d+1);
        }
    }
    cout << (res < 0 ? 0 : res) << endl;
}