#include<iostream>
#include<sstream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<string>
#include<vector>
#include<cmath>
#include<set>
#include<map>
#include<stack>
#include<queue>
#include<numeric>
#include<functional>
#include<complex>

using namespace std;
#define BET(a,b,c) ((a)<=(b)&&(b)<(c))
#define FOR(i,n) for(int i=0,i##_end=(int(n));i<i##_end;i++)
#define SZ(x) (int)(x.size())
#define ALL(x) (x).begin(),(x).end()
#define MP make_pair
#define FOR_EACH(it,v) for(__typeof(v.begin()) it=v.begin(),it_end=v.end() ; it != it_end ; it++)
typedef vector<int> VI;
typedef vector<VI> VVI;

int main()
{
    int x,y,r;
    cin>>x>>y>>r;
    x = abs(x);
    y = abs(y);
    int lower = 0, upper = 100000;
    int ans = 0 ;
    while(lower <= upper){
        int mid = (lower + upper) / 2;
        if(((x + y) / 2.0 * sqrt(2) + r) <= mid * sqrt(2) / 2.0){
            upper = mid - 1;
            ans = mid;
        }else {
            lower = mid + 1;
        }
    }
    cout<<ans<<endl;
    return 0;
}