{programmer:mogtaba amirzade 
url http:\\www.ifjam.com
}
program p11(input,output); {15:repeat form}
var
i,n:integer;
s:longint;
begin
s:=1;
readln(n);
if n=0 then
writeln(s)
else if n<0 then
writeln('no answer')
else
begin
i:=1;
repeat
s:=s*i;
i:=i+1;
until n<i;
writeln(s:1);
end; {if}
readln
end.