type victor=array[1..10000000] of byte;
var i,p,a,b,c:longint;
v,x,y:victor;
n:int64;
zeus:boolean;
f:text;
begin
assign(f,'fact.in');reset(f);
read(f,p);close(f);
if p=0 then n:=1
       else if p<0 then n:=-1
                   else for i:=1 to p do
                                 n:=n+5;
assign(f,'fact.out');rewrite(f);
write(f,n);close(f);
end.