#include <bits/stdc++.h>
int main() {
  float a = 0, b = 0, x = 0, v = 0;
  float y, angle;
  scanf("%f%f%f", &a, &b, &x);
  v = a * a * b - x;
  if (v <= a * a * b / 2) {
    y = v * 2 / (a * a);
    angle = atan(a / y) * 180 / 3.1415926535898;
  } else {
    y = 2 * x / (a * b);
    angle = atan(y / b) * 180 / 3.1415926535898;
  }
  printf("%.10f", 90 - (double)angle);
  return 0;
}
