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*5;
             m:=(i+j) div 2;
            while(i<=j)do
                 begin
                 s:=0;
                 h:=5;
            while(m div h>0)do
                  begin
                  s:=s+(m div h);
                  h:=h*5
                  end;
            if s<p then i:=m-1
                   else j:=m+1;
             m:=(i+j) div 2;
                   end;
            h:=5;
            s:=0;
            m:=m+1;
             while(m div h>0)do
                  begin
                  s:=s+(m div h);
                  h:=h*5
                  end;
            if s=p then writeln(f,m)
                     else writeln(f,-1);
            end;
close(f);
end.