include

using namespace std; int a[10]; int main(){ int n;

cin >> n;
int cnt = 0;
while(n){
	int t = n % 10;
    a[t]++;
    n /= 10;
    cnt++;
}
int ans = 0;
if(cnt%2){
	int k = 0;
    while(!a[k]) k++;
    a[k]--;
    ans = k;
}
int x = 0,y = 0;

while(x<10 && y<10){
	while(x<10 && !a[x]) x++;
    if(x == 10) break;
    a[x]--;
    while(y<10 && !a[y]) y++;
    if(y == 10) break;
    a[y]--;
    ans *= 10;
    ans += x + y;
}
cout << ans;
return 0;

}