Question

Помогите, решите!)))))((((

Answer 1

Var a,n,k: int64;
begin
n:=1;
k:=0;
readln(a);
while a>0 do
begin
k:=k+1;
if (a mod 10 = 4) or (a mod 10 = 7) then
else
begin
n:=0; 
break;
end;
a:=a div 10;
end;
if (n = 1) and ((k = 7) or (k = 4))  then
write('YES')
else
write('NO');
end.