// Wrongri-La Shower

#include<cstdio>

typedef long long ll;

const double EPS = 1e-9;

int X, Y, R;

// -std=c++1y
//double minimum(auto f){
template <typename F>
double minimum(F f){
    double lb = -252521.0, ub = 252521.0;
    for(int i=0;i<100;i++){
        double c1 = 1. * (lb * 2 + ub) / 3, c2 = 1. * (lb + ub * 2) / 3;
    
        if(f(c1) < f(c2)){ub = c2;}
        else{lb = c1;}
    }

    return f(lb);
}

bool can(int k){
    if(minimum([&k](double x){
                double a = x - X, b = x + Y - k;
                return a * a + b * b - R * R;
            }) < EPS){
        return false;
    }

    if(minimum([&k](double x){
                double a = x - X, b = x - Y + k;
                return a * a + b * b - R * R;
            }) < EPS){
        return false;
    }

    if(minimum([&k](double x){
                double a = x - X, b = x - Y - k;
                return a * a + b * b - R * R;              
            }) < EPS){
        return false;
    }

    if(minimum([&k](double x){
                double a = x - X, b = x + Y + k;
                return a * a + b * b - R * R;
            }) < EPS){
        return false;
    }

    return true;
}

int main(){
    scanf("%d %d %d", &X, &Y, &R);

    int lb = X + Y, ub = 252521;
    while(ub - lb > 1){
        int mid = (lb+ub) / 2;
        if(can(mid)){
            ub = mid;
        }else{
            lb = mid;
        }
    }

    printf("%d\n", ub);
}