#include <bits/stdc++.h>
using namespace std;
const double PI=3.14159265358979323846;
int main(){
	double a,b,x;
  	cin >> a >> b >> x;
    cout << fixed << setprecision(15) << atan(x>=a*a*b/2 ? (a*a*b-x)*2/a/a/a : b/(x*2/a/b))/PI*180;
	return 0;
}