#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define REP(i, n)           for(int(i)=0;(i)<(n);++(i))
const int MOD = int(1e9+7);

int N,M,W,H;
int res = 0;

int main(){
    int x,y,d;
    cin >> x >> y >> d;

    int dr = x;
    if(x>d) dr = d;
    int dl = 0;
    if(y<d) dl = d-y;
    res = max(dr-dl+1,0);

    cout << res << endl;
    return 0;
}