var p,nr2,nr5,i,ii:longint;  
    f:text;  
begin  
assign (f,'fact.in');  
reset (f);  
readln (f,p);  
close (f);  
if p=0 then  
begin  
assign (f,'fact.out');  
rewrite (f);  
writeln (f,1);  
close(f);  
end  
else  
begin  
i:=5;  
nr5:=0;  
nr2:=0;  
while (nr5<>p)and(i>0) do  
begin  
ii:=i;  
while ii<>0 do  
if ii mod 5=0 then  
begin  
inc (nr5);  
ii:=ii div 5;  
if ii mod 5=0 then inc(nr2);  
end  
else  
break;  
inc (i,5);  
end;  
if nr5=p then  
begin  
assign (f,'fact.out');  
rewrite (f);  
writeln (f,5*(nr5-nr2));  
close(f);  
end;  
end;  
end.