#include <bits/stdc++.h>
using namespace std;
int main() {
  int A, B, X;
  double result = 0.0;
  double a, b, x;
  double radian = 0.0;
  scanf("%d %d %d", &A, &B, &X);
  a = A;
  b = B;
  x = X;
  if (((a * a * b) / 2) > x) {
    radian = atan(2 * x / (a * b * b));
    result = radian * 180.0 / 3.141592653589793;
    result = fabs(fabs(result) - 90);
  } else {
    radian = atan(-3 * a * a / (2 * (a * a * b - x)));
    result = radian * 180.0 / 3.141592653589793;
    result = fabs(fabs(result) - 90);
  }
_end:
  printf("%12.9lf", result);
  return 0;
}
