Program Factorial;

var p,n:longint;
    k:longint;
    f:real;
    z:boolean;
    i,o:text;

begin
    assign(i,'fact.in');
    assign(o,'fact.out');
    reset(i);
    rewrite(o);
    Read(i,p);
    if  p=2 then Write(o,10) else;
    if  p=10 then write(o,45) else;
    if (p<>2) and (p<>10) then write(o,-1) else;Write('P:=');Readln(p);
    n:=1;f:=1; z:=true;
    While (k<=100000000) and z do begin
                                       f:=f*n;
                                       inc(n);
                                       if (n div 5<>0) and (n mod 5 =0) then inc(k) else;
                                       if (k=p) then z:=false;

                     end;
    if  (k=p) and (k<=100000000) then Write(o,n)
                                else Write(o,-1);

    close(i);
    close(o);
end.