#include <bits/stdc++.h>
#define rep(i, n) REP(i, 0, n)
#define REP(i, l, r) for (int i = l; i < r; ++i)
#define int long long
#ifdef DEBUG
#define dout cout
#else
std::stringstream dout;
#endif
using namespace std;
typedef pair<int, int> P;
struct edge {
  int to, cost;
};
// other libs
int gcd(int a, int b) {
  if (a % b == 0)
    return b;
  else
    return gcd(b, a % b);
}
int lcm(int a, int b) {
  return a * b / gcd(a, b);
}

class dijkstra {
private:
  int V;
  int d[100002];
  priority_queue<P, vector<P>, greater<>> que;

public:
  dijkstra(int v, int s, vector<edge> G[]) {
    V = v;
    update(s, G);
  }

  void update(int s, vector<edge> G[]) {
    fill(d, d + V + 1, 100000000000ll);
    d[s] = 0;
    que.push(make_pair(0, s));
    while (!que.empty()) {
      P p = que.top();
      que.pop();
      int v = p.second;
      if (d[v] < p.first)
        continue;
      rep(i, G[v].size()) {
        edge e = G[v][i];
        if (d[e.to] > d[v] + e.cost) {
          d[e.to] = d[v] + e.cost;
          que.push(make_pair(d[e.to], e.to));
        }
      }
    }
  }

  int find(int e) {
    return d[e];
  }
};
template<typename T>
class Union_Find {
private:
  vector<T> t, s;

public:
  Union_Find(T max_length) {
    rep(i, max_length + 1) {
      t.push_back(i);
      s.push_back(1);
    }
  }

  void Union(T x, T y) {
    if (same(x, y))
      return;
    T tx = Find(x), ty = Find(y);
    if (s[tx] < s[ty]) {
      s[ty] += s[tx];
      t[tx] = ty;
    }
    else if (s[tx] > s[ty]) {
      s[tx] += s[ty];
      t[ty] = tx;
    }
    else if (tx > ty) {
      t[tx] = ty;
      s[ty] += s[tx];
    }
    else {
      t[ty] = tx;
      s[tx] += s[ty];
    }
  }
  T Find(T n) {
    if (t[n] == n)
      return n;
    else
      return t[n] = Find(t[n]);
  }

  bool same(T x, T y) {
    return Find(x) == Find(y);
  }

  T get_Size(size_t a) {
    return s[a];
  }
};
bool ifPrime(int n) {
  if (n == 1)
    return false;
  for (int i = 2; i * i <= n; i++) {
    if (n % i == 0)
      return false;
  }
  return true;
}

set<int> prime_num_factor(int n){
  if(n<2)return set<int>();
  set<int> prime;
  prime.insert(2);
  for(int i=3;i<=n;i++){
    for(int it:prime){
      if(it*it>i){
        prime.insert(i);
        break;
      }
      if(i%it==0)break;
    }
  }
  return prime;
}
vector<int> makeDivisors(int n){
  vector<int> re;
  REP(i,1,sqrt(n)+1){
    if(n%i==0){
      re.push_back(i);
      if(i!=n/i)re.push_back(n/i);
    }
  }
  return re;
}
int modPow(int a,int n,int mod){
  int ret=1;
  while(n){
    if(n&1)ret=ret*a%mod;
    a=a*a%mod;
    n>>=1;
  }
  return ret;
}
bool isOK(double mid,double a,double b,double x){
  double h=a*tan(mid/180*3.141592653589793238462643383279);
  if(0.0<=x-a*a*h/2.0){
    h+=(x-a*a*h/2.0)/(a*a);
    return h<=b;
  }
  else{
    return a*b*b/tan(mid/180*3.141592653589793238462643383279)/2.0>=x;
  }
}
double binary_search(double ok,double ng,double a,double b,double x){
  while(abs(ok-ng)>=0.00000001){
    double mid=(ok+ng)/2;
    if(isOK(mid,a,b,x))ok=mid;
    else ng=mid;
  }
  return ok;
}
signed main(signed argc, char* argv[]) {
  double a,b,x;
  cin>>a>>b>>x;
  printf("%.10lf\n",binary_search(0,90,a,b,x));
}


Measured memory_bytes: 256