import std.conv, std.functional, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.container, std.math, std.numeric, std.range, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum LIM = 300;

int F, N, K;

void main() {
  auto binom = new real[][LIM];
  foreach (n; 0 .. LIM) {
    binom[n] = new real[n + 1];
    binom[n][0] = binom[n][n] = 1;
    foreach (k; 1 .. n) {
      binom[n][k] = binom[n - 1][k - 1] + binom[n - 1][k];
    }
  }
  
  try {
    for (; ; ) {
      F = readInt();
      N = readInt();
      K = readInt();
      
      auto pw = new real[][](F + 1, N + 1);
      foreach (i; 0 .. F + 1) {
        pw[i][0] = 1.0;
        foreach (j; 1 .. N + 1) {
          pw[i][j] = pw[i][j - 1] * (1.0 * i / F);
        }
      }
      
      real ans = 0.0;
      foreach (f; 1 .. F + 1) {
        foreach (a; 0 .. N) {
          foreach (b; 0 .. a + 1) {
            const c = K - 1 - b;
            if (0 <= c && c <= N - 1 - a) {
              // b dice >= f in [0, a)
              // c dice >  f in (a, N)
              real prob = pw[1][1];
              prob *= binom[a][b];
              prob *= binom[N - 1 - a][c];
              prob *= pw[F - f + 1][b];
              prob *= pw[f - 1][a - b];
              prob *= pw[F - f][c];
              prob *= pw[f][N - 1 - a - c];
              ans += prob * f;
            }
          }
        }
      }
      writefln("%.10f", ans);
    }
  } catch (EOFException e) {
  }
}