// ki bood ke goft Ghatinga?

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef pair<pii,int> ppiii;

// vectors and Sets:
#define vc vector
#define pb push_back
#define all(c) (c).begin(), (c).end()

// pairs
#define mp make_pair
#define fr first
#define sc second

// execution time check and Debug
#define StartEX clock_t startExeTime = clock();
#define EndEX clock_t endExeTime = clock();
#define ExTime cerr << "\nTotal Execution Time is: " << double(-double(startExeTime)+double(endExeTime)) / CLOCKS_PER_SEC;
#define debug(x) cerr << #x << " : " << x << '\n'
#define endl "\n"

// time optimization
#define Heh ios::sync_with_stdio(false);cin.tie(0);
#define Bah ios::sync_with_stdio(false);
#pragma GCC optimize("Ofast")
// #pragma GCC target("avx,avx2,fma")

// useful functions
ll pw(ll a,ll b){
  ll ret = 1;
  ll mul = a;
  while(b > 0){
	if(b&1)
	  ret = (ret * mul);
	mul = (mul * mul);
	b >>= 1;
  }
  return ret;
}
ll pw(ll a,ll b,ll mod){
  ll ret = 1;
  ll mul = a;
  while(b > 0){
	if(b&1)
	  ret = (ret * mul) % mod;
	mul = (mul * mul) % mod;
	b >>= 1;
  }
  return ret;
}

ll to_int(string s){
  ll ret = 0;
  for(int i = 0 ; i < (int)s.size() ; i++) ret = 10 * ret + s[i] - '0';
  return ret;
}

bool deq(ld a , ld b){return (abs(a-b) < 0.000001);} // 10 ^ -6

ld f(ld a , ld b , ld p){
  ld ret = 0;
  ld l = min(max((ld)0 , b - a) , p);
  ret += a * l + l * l / 2;
  ret += b * (p - l);
  ret /= p;
  return ret;
}

int main()
{
  int r , c;
  cin >> r >> c;
  ld p;
  cin >> p;
  ld dp[r][c] = {};
  for(int i = r - 1 ; i >= 0 ; i--){
    for(int j = c - 1 ; j >= 0 ; j--){
      if(i == r-1 and j == c-1) continue;
      ld a = 1e18 , b = 1e18;
      if(i != r-1) a = dp[i+1][j];
      if(j != c-1) b = dp[i][j+1];
      dp[i][j] = (ld)1/2 * f(a , b , p) + (ld)1/2 * f(b , a , p);
    }
  }
  cout << fixed << setprecision(10) << dp[0][0] << endl;
}

// ki seda kard Patinga?