#include <bits/stdc++.h>
int main(void) {
  long double a, b, x;
  long double y;
  long double l = 0, m, h = 90.0;
  scanf("%lf%lf%lf", &a, &b, &x);
  for (int i = 0; i < 100; i++) {
    m = (h + l) / 2.0;
    if (a * b / 2.0 < x) {
      y = a * b - a * a * 0.5 * tan(m * M_PI / 180.0);
    } else {
      y = b * b * 0.5 * tan((90.0 - m) * M_PI / 180.0);
    }
    if (x > y * a) {
      h = m;
    } else {
      l = m;
    }
  }
  printf("%.10llf", m);
}
