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

signed main(){
  int X, Y, R; cin >> X >> Y >> R;
  for( int i = 1; ; ++i ){
    double t = 1.0 * ( abs( X ) + abs( Y ) - i ) / sqrt( 2 );
    if( t >= R )
      cout << i << endl,
      exit( 0 );
  }
  return 0;
}