i,j,k,n,x:longint;
a,b,c,d,e,p:real;

readln (n);
readln(x);
readln(p);
a:=1;b:=1;c:=1;d:=1;e:=1;
for i:=1 to n do
a:=a*i;
for j:=1 to x do
begin
b:=b*j;
c:=c*p;
end;
for k:=1 to (n-x) do
begin
d:=d*k;
e:=e*(1-p);
end;
writeln(a/(b*d)*c*e:0:4);