D.cpp

// #pragma GCC optimize("Ofast,unroll-loops")
// #pragma GCC target("avx,avx2,fma")

#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define ull unsigned long long
#define dd double
#define ld long double
#define sl(n) scanf("%lld", &n)
#define si(n) scanf("%d", &n)
#define sd(n) scanf("%lf", &n)
#define pll pair <ll, ll>
#define pii pair <int, int>
#define mp make_pair
#define pb push_back
#define all(v) v.begin(), v.end()
#define inf (1LL << 61)
#define loop(i, start, stop, inc) for(ll i = start; i <= stop; i += inc)
#define for1(i, stop) for(ll i = 1; i <= stop; ++i)
#define for0(i, stop) for(ll i = 0; i < stop; ++i)
#define rep1(i, start) for(ll i = start; i >= 1; --i)
#define rep0(i, start) for(ll i = (start-1); i >= 0; --i)
#define ms(n, i) memset(n, i, sizeof(n))
#define casep(n) printf("Case %lld:", ++n)
#define pn printf("\n")
#define pf printf
#define EL '\n'
#define fastio std::ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);

const ll sz = 105;
double dp[sz][sz][sz];
bool check[sz][sz][sz];

double solve(ll a, ll b, ll c)
{
    if(a >= 100 || b >= 100 || c >= 100)
        return 0;

    bool &chk = check[a][b][c];
    double &ret = dp[a][b][c];
    if(chk)
        return ret;

    chk = 1, ret = 0;
    double tot = a+b+c;

    if(a > 0) ret += a/tot*(1 + solve(a+1, b, c));
    if(b > 0) ret += b/tot*(1 + solve(a, b+1, c));
    if(c > 0) ret += c/tot*(1 + solve(a, b, c+1));

    return ret;
}

int main()
{
    ll a, b, c;
    cin >> a >> b >> c;

    cout << setprecision(7) << fixed << solve(a, b, c) << EL;

    return 0;
}