/*
ZADATAK: meteor
JEZIK: C++
*/
#include <iostream.h>
#include <fstream.h>

const long int MAX=2*1000000 +4;

long le[MAX],de[MAX];
long x,y,r;

void centar(long tx, long ty, long &x1, long &y1){
	int zx=1, zy=1;
	if (tx<0) {zx=-1; tx=-tx;}
	if (ty<0) {zy=-1; ty=-ty;}
	x1=(tx/100)*100+50;
	y1=(ty/100)*100+50;

	if (tx%100==0 && x1>x) x1-=100;
	if (ty%100==0 && y1>y) y1-=100;

	x1=zx*x1;
	y1=zy*y1;
}

void minim(long &x, long y){
	if (y<x) x=y;
}
void maxim(long &x, long y){
	if (y>x) x=y;
}

int ukrugu_t( long tx, long ty){
	if ( (tx-x)*(tx-x) + (ty-y)*(ty-y) < r*r )
		return 1;
	return 0;
}

int ukrugu( long tx, long ty ){
	if ( ukrugu_t( tx-50 , ty-50 ) ) return 1;
	if ( ukrugu_t( tx-50 , ty+50 ) ) return 1;
	if ( ukrugu_t( tx+50 , ty-50 ) ) return 1;
	if ( ukrugu_t( tx+50 , ty+50 ) ) return 1;
	return 0;
}

int main(){

	//ifstream fin("zad1.txt");
	double xdo,ydo,rdo;
	//fin>>xdo>>ydo>>rdo;
	cin>>xdo>>ydo>>rdo;
	x=long(xdo*100); y=long(ydo*100); r=long(rdo*100);
	//fin.close();

	long x1,y1,xl,xd,yg,yd,yi;
	x1=0; y1=0;

	centar(x-r,y-r,xl,yd);
	centar(x+r,y+r,xd,yg);

//	cout<<xl<<" "<<xd<<endl<<yg<<" "<<yd<<endl<<endl;

	for (yi=yd;yi<=yg;yi+=100) {
		le[yi/100]=xd; de[yi/100]=xl;
	}

	centar(x,y+r,x1,y1);
	char kudax='d', kuday='d';

	//int d=0;
	do{
		//cout<<x1<<" "<<y1<<endl;
		//d++;
		//if (d>20) break; // !!!!!!!!

		minim(le[y1/100],x1);
		maxim(de[y1/100],x1);

		if (kudax=='d' && kuday=='d'){
			if ( ukrugu( x1+100, y1 ) ){
				x1+=100;
			} else
			if ( ukrugu( x1+100, y1-100 ) ){
				x1+=100; y1-=100;
			} else
			if ( ukrugu( x1, y1-100 ) ){
				y1-=100;
			} else {
				kudax='l'; kuday='d';
			}
		} else
		if (kudax=='l' && kuday=='d'){
			if ( ukrugu( x1, y1-100 ) ){
				y1-=100;
			} else
			if ( ukrugu( x1-100, y1-100 ) ){
				x1-=100; y1-=100;
			} else
			if ( ukrugu( x1-100, y1 ) ){
				x1-=100;
			} else {
				kudax='d'; kuday='g';
			}
		} else if (kudax=='d' && kuday=='g'){
			if ( ukrugu( x1-100, y1+100 ) ){
				x1-=100; y1+=100;
			} else
			if ( ukrugu( x1, y1+100 ) ){
				y1+=100;
			} else
			if ( ukrugu( x1+100, y1+100 ) ){
				x1+=100; y1+=100;
			} else {
				kudax='k'; kuday='g';
			}
		}
			

	} while (kudax!='k');


	long long rez=0; //!!!!!!!!!!

	//cout<<endl;
	for (yi=yd;yi<=yg;yi+=100) {
	//	cout<<double(yi)/100<<" "<<le[yi/100]<<" "<<de[yi/100]<<endl;
		rez+= (de[yi/100]-le[yi/100]+100)/100;
	}

	cout<<rez<<endl;

	return 0;
}