//Author: Kevin
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
#define ll long long
#define ull unsigned ll
#define pb emplace_back
#define mp make_pair
#define ALL(x) (x).begin(),(x).end()
#define rALL(x) (x).rbegin(),(x).rend()
#define srt(x) sort(ALL(x))
#define rev(x) reverse(ALL(x))
#define rsrt(x) sort(rALL(x))
#define sz(x) (int)(x.size())
#define inf 0x3f3f3f3f
#define pii pair<int,int>
#define lb(v,x) (int)(lower_bound(ALL(v),x)-v.begin())
#define ub(v,x) (int)(upper_bound(ALL(v),x)-v.begin())
#define uni(v) v.resize(unique(ALL(v))-v.begin())
#define longer __int128_t
void die(string S){puts(S.c_str());exit(0);}
long double dp[1005][1005];
ll p;
int n,m;
long double solve(long double a,long double b,long double c)
{
	if(b<a) return b;
	if(a+c<b) return a+c/2.0;
	long double val=b-a;
	return (a+val/2.0)*val/c+(c-val)*b/c;
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>n>>m>>p;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=m;j++)
		{
			if(i==1&&j==1) continue;
			if(i==1)
				dp[i][j]=dp[i][j-1]+p*0.25;
			else if(j==1)
				dp[i][j]=dp[i-1][j]+p*0.25;
			else
				dp[i][j]=(solve(dp[i-1][j],dp[i][j-1],p)+solve(dp[i][j-1],dp[i-1][j],p))*0.5;
		}
	cout<<fixed<<setprecision(15)<<dp[n][m]<<endl;
	return 0;
}