import java.io.*;
import java.util.*;

public class spiro {
	private static final Scanner cin = new Scanner(System.in);

	public static void main(String[] args) {
		while(true) {
			int p = cin.nextInt();
			int q = cin.nextInt();
			int r = cin.nextInt();

			if(p == 0 && q == 0 && r == 0) { break; }

			double l;

			if(r != 0) {
				l = new Integrator(p, q, r).integrate();
			}
			else {
				l = 2.0 * Math.PI * (p - q);
			}

			System.out.println(String.format("%.8f", l));
		}
	}

	private static class Integrator {
		private static int N = 1048576;

		private double a;
		private double b;
		private double m;
		private double T;

		public Integrator(int p, int q, int r) {
			double dp = p;
			double dq = q;
			double dr = r;

			double v1 = dp - dq;
			double v2 = v1 / dq * dr;

			a = v1 * v1 + v2 * v2;
			b = v1 * v2 * 2.0;
			m = dq / dp;
			T = dp / gcd(q, p - q) * 2.0 * Math.PI;
		}

		public double integrate() {
			double l = 0.0;

			for(long i = 0; i < N; i++) {
				double x1 = T * (i + 0) / N;
				double x2 = T * (i + 1) / N;
				double xm = (x1 + x2) / 2.0;
				l += Math.sqrt(a - b * Math.cos(x1));
				l += Math.sqrt(a - b * Math.cos(xm)) * 4.0;
				l += Math.sqrt(a - b * Math.cos(x2));
			}

			return l * m * T / (6 * N);
		}

		private static int gcd(int a, int b) {
			return (b == 0) ? a : gcd(b, a % b);
		}
	}
}