#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define DUMP(x) cout << #x << " = " << (x) << endl;
#define FOR(i, m, n) for (ll i = m; i < n; i++)
#define IFOR(i, m, n) for (ll i = n - 1; i >= m; i--)
#define REP(i, n) FOR(i, 0, n)
#define IREP(i, n) IFOR(i, 0, n)
#define FOREACH(x, a) for (auto&(x) : (a))
#define ALL(v) (v).begin(), (v).end()
#define SZ(x) ll(x.size())

int main() {
  vector<ll> p(3);
  ll b = 0;
  REP(i, 3) {
    cin >> p[i];
    b += p[i];
  }
  ll ans = 0;
  REP(i, 3) {
    ans = max(ans, p[i]);
    ans = max(ans, b - p[i]);
  }
  double ans2 = ans / (1.0 * b);
  cout << fixed << setprecision(10);
  cout << ans2 << endl;
}