var
p,i,aux,exp:longint;
f,g:text;
begin
        assign(f,'fact.in');reset(F);
        ASSIGN(G,'fact.out');rewrite(g);
        readln(f,p);
        if p=0 then writeln(g,1);
        i:=p*5;
        while exp<p do begin
                        i:=i-5;
                        exp:=i div 5+i div 25+i div 125+i div 625+i div 3125+i div 15625+i div 78125+i div 390625
                +i div 1953125+i div 9765625+i div 48828125+i div 244140625;
        end;
        if exp>p then writeln(g,-1)
        else writeln(g,i);
        close(F);
        close(g);
end.