#include <bits/stdc++.h>
using namespace std;

signed main(){
  int x, y, d; cin >> x >> y >> d;
  x = min( x, d );
  y = min( y, d );
  if( not ( x >= y ) )
    swap( x, y );
  int a = -1;
  int lb = 0, rb = x;
  while( lb <= rb ){
    int mid = lb + rb >> 1;
    if( mid + y >= d )
      a = mid, rb = mid - 1;
    else
      lb = mid + 1;
  }
  if( a == -1 ) cout << 0 << endl, exit( 0 );
  cout << x - a + 1 << endl;
  return 0;
}