Program fact;
 var p,i:longint;
     f,n:longint;
     a:array[1..100] of longint;
     fi,fo:text;
 begin
 assign(fi,'fact.in');reset(fi);
 assign(fo,'fact.out');rewrite(fo);
 read(fi,p);
 repeat
 begin
 n:=0;f:=1;
 inc(i);
 while (f<i) do begin
 f:=f*5;
 n:=n+i div f;
 end;
 if n>p then break;
 end;
 until (n=p);
 if n>p then write(fo,'-1') else
 writeln(fo,i);
 close(fo);
 end.