var n,ret,data;       
  
procedure myproc; 
var save; 
begin 
  if n=1 then ret:=1; 
  if n>1 then begin 
     save:=n; 
     n:=n-1; 
     call myproc; 
     n:=save; 
     ret:=ret*n; 
  end; 
end; 
  
begin 
  read(n); 
  call myproc; 
  write(ret); 
end.