/*
ZADATAK: meteor
JEZIK: c
*/

#include <stdio.h>
#include <math.h>

#define floattype double
#define breaks 100000000
#define step 8
#define eps 1E-10

FILE *inFile, *outFile;
floattype Cx, Cy, R;
long rez, rezV;

void ucitavanje() {
	fscanf(inFile, "%lf %lf %lf", &Cx, &Cy, &R);
	Cx -= (long)Cx;
	Cy -= (long)Cy;
}

int jednako(floattype a, long b) {
	if (fabs(a - (floattype)b) < eps) return 1;
	else return 0;
}

// nalazi najveci ceo broj manji od datog broja
long findmax(floattype value) {
	long ret;
	if (value > 0)
	{
		ret = (long) value;
		if (jednako(value, ret)) ret--;
	}
	else ret = (long) (value - 1);
	return ret;
}

// nalazi najveci ceo broj ne veci od datog broja
long findmin(floattype value) {
	long ret;
	if (value >= 0) ret = (long) value;
	else
	{
		ret = (long) (value - 1);
		if (jednako(value, ret + 1)) ret++;
	}
	return ret;
}

void obrada() {
// deklaracije promenljivih
	floattype maxX, maxY, minX, minY, d, Xmin, Xmax;
	long maxIX, maxIY, minIX, minIY, CIy, yI, XminI, XmaxI;

// odredjivanje granica
	maxY = Cy + R;
	minY = Cy - R;
	maxX = Cx + R;
	minX = Cx - R;
	maxIY = findmax(maxY);
	minIY = findmin(minY);
	maxIX = findmax(maxX);
	minIX = findmin(minX);
	CIy = findmax(Cy);

// izracunavanje - glavni deo
	rez = maxIX - minIX + 1;
	rezV = 0;
	for (yI = CIy + 1; yI <= maxIY; yI++)
	{
		d = pow(pow(R, 2) - pow(yI - Cy, 2), 0.5);
		Xmin = Cx - d;
		Xmax = Cx + d;
		XmaxI = findmax(Xmax);
		XminI = findmin(Xmin);
		rez += XmaxI - XminI + 1;
		if (rez >= breaks)
		{
			rezV += rez / breaks;
			rez = rez % breaks;
		}
	}
	for (yI = CIy - 1; yI >= minIY; yI--)
	{
		d = pow(pow(R, 2) - pow(yI + 1 - Cy, 2), 0.5);
		Xmin = Cx - d;
		Xmax = Cx + d;
		XmaxI = findmax(Xmax);
		XminI = findmin(Xmin);
		rez += XmaxI - XminI + 1;
		if (rez >= breaks)
		{
			rezV += rez / breaks;
			rez = rez % breaks;
		}
	}
}

void stampanje() {
	long i, b = breaks;
	if (rezV > 0)
	{
		fprintf(outFile, "%ld", rezV);
		for (i = 0; i < step; i++)
		{
			b /= 10;
			fprintf(outFile, "%ld", rez / b);
			rez = rez % b;
		}
		fprintf(outFile, "\n");
	}
	else fprintf(outFile, "%ld\n", rez);
}

long main() {
	inFile = stdin;//fopen("meteor.in", "r");
	outFile = stdout;//fopen("meteor.out", "w");

	ucitavanje();
	obrada();
	stampanje();

//	  fclose(inFile);
//	  fclose(outFile);

	return 0;
}