#include <bits/stdc++.h>
using namespace std;
int main() {
  cout << fixed << setprecision(10);
  long double a, b, x, y;
  long double c = 45.0;
  cin >> a >> b >> x;
  if (x > b * a * a / 2.0) {
    y = 2.0 * (b - x / (a * a)) / a;
  } else {
    y = a * b * b / x;
  }
  cout << atan(y) / atan(1) * c;
}
