void perfect(int a, int b)
{
int np=0, num, j;
if (a%2==1) ++a;
if (b%2==1) --b;
for (num=b; num>=a; num-=2) {
int suma=0;
for (j=1; j<=num/2; ++j)
if (num%j==0) suma+=j;
if (suma==num) { ++np; cout << num << " " ;}
}
if (np==0) cout << "nu exista" << "\n";
return;
}