var p,nr,s,n:longint;   
begin  
assign(input,'fact.in');reset(input);   
assign(output,'fact.out');rewrite(output);   
readln(p);   
s:=0;   
nr:=0;   
if p=0 then s:=1 else  
if p=5 then s:=-1 else  
begin  
while nr<>p do begin  
  s:=s+5; inc(nr);   
if (s mod 25=0) and (nr<>p) then begin  
   n:=s div 5; inc(nr);   
 while (n div 5 mod 5=0) and (nr<>p) do begin  
    n:=n div 5; inc(nr); end;   
  end;   
 end;   
end;   
write(s);   
close(input);close(output);   
end.