var f,g:text;
    p,n,pp:1..100000000;
begin
assign(f,'fact.in');reset(f);
assign(g,'fact.out');rewrite(g);
readln(f,p);
{while p-pp>61035144 do begin
        pp:=pp+61035156;
        n:=n+244140625;
end;}
while p-pp>12207020 do begin
        pp:=pp+12207031;
        n:=48828125+n;
end;
while p-pp>2441396 do begin
        pp:=pp+2441406;
        n:=9765625+n;
end;
while p-pp>488272 do begin
        pp:=pp+488281;
        n:=1953125+n;
end;
while p-pp>97648 do begin
        pp:=pp+97656;
        n:=390625+n;
end;
while p-pp>19524 do begin
        pp:=pp+19531;
        n:=78125+n;
end;
while p-pp>3900 do begin
        pp:=pp+3906;
        n:=15625+n;
end;

while p-pp>776 do begin
        pp:=pp+781;
        n:=3125+n;
end;
while p-pp>152 do begin
        pp:=pp+156;
        n:=625+n;
end;
while p-pp>28 do begin
        pp:=pp+31;
        n:=125+n;
end;
while p-pp>4 do begin
        pp:=pp+6;
        n:=25+n;
end;
while p-pp>0 do begin
        pp:=pp+1;
        n:=5+n;
end;
if p=0 then n:=1;
if p=pp then write(g,n)
        else write(g,-1);

close(g);
end.