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

int main(void) {
	int x, y, r, tmp;
	scanf("%d%d%d", &x, &y, &r);

	x = abs(x);
	y = abs(y);
	if(x < y){
		tmp = x;
		x = y;
		y = tmp;
	}
	printf("%d\n", (int)((sqrt(y * y * 2) + r) / sqrt(2) * 2 + x - y + 1));
	return 0;
}