#include <bits/stdc++.h>
#define _rep(i, x, y) for(int i = x; i <= y; ++i)
#define _req(i, x, y) for(int i = x; i >= y; --i)
#define _rev(i, u) for(int i = head[u]; i; i = e[i].nxt)
#define pb push_back
#define fi first
#define se second
#define mst(f, i) memset(f, i, sizeof f)
using namespace std;

template<typename T> void debug(string s, T x) {cerr << " " << s << " = " << x << " \n";}
template<typename T, typename... Args> void debug(string s, T x, Args... args) {for (int i = 0, b = 0; i < (int)s.size(); i++) if (s[i] == '(' || s[i] == '{') b++;else if (s[i] == ')' || s[i] == '}') b--;else if (s[i] == ',' && b == 0) {cerr << " " << s.substr(0, i) << " = " << x << " |";debug(s.substr(s.find_first_not_of(' ', i + 1)), args...);break;}}
#ifdef ONLINE_JUDGE
#define Debug(...)
#else
#define Debug(...) debug(#__VA_ARGS__, __VA_ARGS__)
#endif

// #ifdef ONLINE_JUDGE
// #define debug(...) 0
// #else
// #define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
// #endif
typedef long long ll;
typedef pair<int, int> PII;
namespace fastio{
#ifdef ONLINE_JUDGE
	char ibuf[1 << 20],*p1 = ibuf, *p2 = ibuf;
#define get() p1 == p2 && (p2 = (p1 = ibuf) + fread(ibuf, 1, 1 << 20, stdin), p1 == p2) ? EOF : *p1++
#else
#define get() getchar()
#endif
	template<typename T> inline void read(T &t){
		T x = 0, f = 1;
		char c = getchar();
		while(!isdigit(c)){
			if(c == '-') f = -f;
			c = getchar();
		}
		while(isdigit(c)) x = x * 10 + c - '0', c = getchar();
		t = x * f;
	}
	template<typename T, typename ... Args> inline void read(T &t, Args&... args){
		read(t);
		read(args...);
	}
	template<typename T> void write(T t){
		if(t < 0) putchar('-'), t = -t;
		if(t >= 10) write(t / 10);
		putchar(t % 10 + '0');
	}
	template<typename T, typename ... Args> void write(T t, Args... args){
		write(t), putchar(' '), write(args...);
	}
	template<typename T> void writeln(T t){
		write(t);
		puts("");
	}
	template<typename T> void writes(T t){
		write(t), putchar(' ');
	}
#undef get
};
using namespace fastio;
#define multitest() int T; read(T); _rep(tCase, 1, T)
namespace Calculation{
	const ll mod = 998244353;
	ll ksm(ll p, ll h){ll base = p % mod, res = 1; while(h){if(h & 1ll) res = res * base % mod; base = base * base % mod, h >>= 1ll;} return res;}
	void dec(ll &x, ll y){x = ((x - y) % mod + mod) % mod;}
	void add(ll &x, ll y){x = (x + y) % mod;}
	void mul(ll &x, ll y){x = x * y % mod;}
	ll sub(ll x, ll y){return ((x - y) % mod + mod) % mod;}
	ll pls(ll x, ll y){return ((x + y) % mod + mod) % mod;}
	ll mult(ll x, ll y){return x * y % mod;}
}
using namespace Calculation;
const int N = 1005;
int n, m;
double f[N][N], p;

int main(){
	read(n, m), scanf("%lf", &p);
	double invp = 1.0 / p;
	// f[1][1] = 0;
	_req(i, n, 1){
		_req(j, m, 1){
			if(i == n && j == m) continue;
			if(i < n && j < m) {
				double a = f[i][j + 1], b = f[i + 1][j];
				if(a > b) swap(a, b);
				double res = 0;
				if(b >= a + p) {
					res = a + p / 4.;
				} else {
					res = (b - a) / p * (a + b) / 2.;
					res += (p - b + a) / p * (b);
					res += a;
					res /= 2;
				}
				f[i][j] += res;
			}else if(i == n){
				f[i][j] = f[i][j + 1] + p / 4.00;
			}else{
				f[i][j] = f[i + 1][j] + p / 4.00;
			}
		}
	}
	printf("%.10lf\n", f[1][1]);
	return 0;
}