#include <bits/stdc++.h>
using namespace std;
#define REP(i,a,n) for(int i=(a); i<(int)(n); i++)
#define rep(i,n) REP(i,0,n)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin(); it!=(c).end(); ++it)
#define ALLOF(c) (c).begin(), (c).end()
typedef long long ll;
typedef unsigned long long ull;


int main(){
  int L, R, M;
  cin >> L >> R >> M;

  if(R < M){
    cout << R-(L-1) << endl;
  }else{
    if(L < R-M) cout << M << endl;
    else cout << min(M, R-(L-1)) << endl;
  }
  
  return 0;
}