program alex;
var f:text;
    i,j,p,m,s,h,d:longint;
begin
assign(f,'fact.in');reset(f);
readln(f,p);
close(f);
assign(f,'fact.out');rewrite(f);
if p=0 then writeln(f,1)
       else begin
            i:=1;
            j:=p;
            while(i<=j)and(s<>p)do
                 begin
                 m:=(i+j) div 2;
                 s:=0;
                 h:=1;
                 d:=m*5;
            while(d div h<>0)do
                  begin
                  h:=h*5;
                  s:=s+(d div h);
                  end;
            if s<p then i:=m
                   else j:=m;
            if m*5=p then writeln(f,m*5)
                     else writeln(f,-1);
                     end;
            end;
close(f);
end.