var f,g:text;
i,a,b,c:longint;
x,s:real;
begin
assign(f,'secv5.in');
reset(f);
readln(f,a,b,c);
close(F);
s:=1;
for i:=2 to b do
s:=s*i;
x:=s;
for i:=b+1 to c do
x:=x*i;
assign(f,'secv5.out');
rewrite(f);
writeln(f,x+s:0:0);
close(f);
end.