import std.stdio, std.conv, std.functional, std.string; import std.algorithm, std.array, std.container, std.range, std.typecons; import std.numeric, std.math, std.random; import core.bitop; string FMT_F = "%.10f"; static string[] s_rd; T RD(T = long)() { while(!s_rd.length) s_rd = readln.chomp.split; string res = s_rd[0]; s_rd.popFront; return res.to!T; } string RDR()() { return readln.chomp; } T[] ARR(T = long)(in string str, T fix = 0) { auto r = str.split.to!(T[]); r[] += fix; return r; } size_t[] MAKE_IDX(alias less = "a < b", Range)(Range range) { auto idx = new size_t[](range.length); makeIndex!(less)(range, idx); return idx;} size_t MIN_POS(alias less = "a < b", Range)(Range range) { auto r = minPos!(less)(range); return range.length - r.length; } bool inside(T)(T x, T b, T e) { return x >= b && x < e; } bool minimize(T)(ref T x, T y) { if (x > y) { x = y; return true; } else { return false; } } bool maximize(T)(ref T x, T y) { if (x < y) { x = y; return true; } else { return false; } } long mod = 10^^9 + 7; void moda(ref long x, long y) { x = (x + y) % mod; } void mods(ref long x, long y) { x = ((x + mod) - (y % mod)) % mod; } void modm(ref long x, long y) { x = (x * y) % mod; } void main() { auto N = RD; auto p = RD!double; auto q = RD!double; double ans = 0.0; auto dp = new double[2][](N+1); dp[0][0] = 1.0; dp[0][1] = 1.0; foreach (i; 0..N) { dp[i+1][0] = dp[i][0] * q; dp[i+1][1] = dp[i][0] * p; ans += dp[i+1][1] * dp[i][0]; if (i > 0) { ans += dp[i+1][1]^^2 * dp[i][1] * dp[i][0]; } if (i > 1) { ans += dp[i+1][1] * dp[i][0] * dp[i][1] * dp[i-1][1]; } } writefln(FMT_F, ans); stdout.flush(); debug readln(); }