#include <bits/stdc++.h>
using namespace std;
int main() {
  double a, b, x;
  cin >> a >> b >> x;
  double normal = x / a;
  double all = a * b;
  if (all / 2 >= normal) {
    cout << 90 - atan(2 * x / a / b / b) * 180 / M_PI;
  } else {
    double re = 2 * x;
    double su = a * a * b;
    double lt = re - su;
    cout << 90 - atan(a * a * a / lt) * 180 / M_PI;
  }
}
