#include <bits/stdc++.h>

using namespace std;

#define iter(v) v.begin(), v.end()
#define SZ(v) int(v.size())
#define pb emplace_back
#define ff first
#define ss second

using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;

#ifdef zisk
void debug(){cerr << "\n";}
template<class T, class ... U>
void debug(T a, U ... b){ cerr << a << " ", debug(b...); }
template<class T> void pary(T l, T r){
	while(l != r) cerr << *l << " ", l++;
	cerr << "\n";
}
#else
#define debug(...) void()
#define pary(...) void()
#endif

template<class A, class B>
ostream& operator<<(ostream& o, pair<A, B> p){
	return o << '(' << p.ff << ',' << p.ss << ')';
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	int r,c;
	double p;
	cin >> r >> c >> p;
	vector<vector<double> > dp(r,vector<double>(c));
	for(int i=r-1;i>=0;i--){
		for(int j=c-1;j>=0;j--){
			if(i==r-1 && j==c-1){
				continue;
			}
			if(i==r-1){
				dp[i][j]=dp[i][j+1]+p/4;
			}
			else if(j==c-1){
				dp[i][j]=dp[i+1][j]+p/4;
			}
			else{
				if(dp[i][j+1]<=dp[i+1][j]){
					dp[i][j]+=dp[i][j+1]/2;
					double u=dp[i+1][j]-dp[i][j+1];
					u=min(u,p);
					dp[i][j]+=(p-u)/p*dp[i+1][j]/2;
					dp[i][j]+=u/p/2*(dp[i][j+1]+u/2);
				}
				else{
					dp[i][j]+=dp[i+1][j]/2;
					double u=dp[i][j+1]-dp[i+1][j];
					u=min(u,p);
					dp[i][j]+=(p-u)/p*dp[i][j+1]/2;
					dp[i][j]+=u/p/2*(dp[i+1][j]+u/2);
				}
				//debug(i,j,dp[i][j]);
			}
		}
	}
	for(int i=0;i<r;i++){
		//pary(iter(dp[i]));
	}
	cout << fixed << setprecision(12) << dp[0][0] << "\n";
}