// D - Water Bottle
#include <bits/stdc++.h>
using namespace std;
using dbl = double;

int main(){
	dbl a,b,x; cin>>a>>b>>x;
	dbl s = x/a;
	dbl h = b, w = a;
	if(s < a*b/2) w = s/b*2;
	else h = (b-s/a)*2;
	printf("%.10f\n", atan2(h, w)*180/M_PI);
}