#include <iostream>
#include <cmath>
#include <cstdio>
using namespace std;
double a,b,c;
double ans = 0;
int cnt = 50000;
int main() {
cin >> a >> b >> c;
while(cnt--) {
double f_prime_x = a + b*cos(ans);
double f_x = a * ans + b * sin(ans) - c;
ans = (f_prime_x*ans - f_x) / f_prime_x;
}
printf("%.11f",ans);
}