#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
  double a, b, x, c, tmp;
  double pi = 3.1415926535;
  cin >> a >> b >> x;
  c = 45.0;
  tmp = a * a * (b - (a / (2.00000 * tan(c / 180.00000 * pi))));
  if (tmp <= x) {
    for (c = 0; c <= 45; c = c + 0.000001) {
      tmp = a * a * (b - (a / (2.00000 * tan(c / 180.00000 * pi))));
      if (tmp <= x && tmp + 0.000001 >= x) {
        break;
      }
    }
  } else {
    for (c = 45; c <= 90; c = c + 0.000001) {
      tmp = a * a * (b - (a / (2.00000 * tan(c / 180.00000 * pi))));
      if (tmp <= x && tmp + 0.000001 >= x) {
        break;
      }
    }
  }
  cout << 90.00000 - c << endl;
}
