#include <bits/stdc++.h>
#define st first
#define nd second
using lint = long long;
constexpr int mod = 998244353;
constexpr int inf = 0x3f3f3f3f;
constexpr lint linf = 0x3f3f3f3f3f3f3f3f;
using namespace std;

using dbl = double;

int main(){
    cin.tie(nullptr)->sync_with_stdio(false);
    int n, m, p;
    cin>>n>>m>>p;
    vector<vector<dbl>>dp(n+1, vector<dbl>(m+1));
    for(int i=1;i<=n;i++){
        for(int j=1;j<=m;j++){
            if(i == 1 && j == 1) continue;
            if(j > 1 && i > 1){
                dbl d = abs(dp[i-1][j] - dp[i][j-1]);
                dbl mn = min(dp[i-1][j], dp[i][j-1]);
                dp[i][j] = (d * d / 2 + (p - d) * d) / p / 2 + mn;
            }
            else if(j > 1){
                dp[i][j] = dbl(p) / 4 + dp[i][j-1];
            }
            else{
                dp[i][j] = dbl(p) / 4 + dp[i-1][j];
            }
        }
    }
    cout<<fixed<<setprecision(8);
    cout<<dp[n][m]<<"\n";
    return 0;
}