#include <cstdlib>
#include <iostream>
#include <cmath>
#include <algorithm>

using namespace std;

int main() {
    long long n,c;

    cin >> n;
    c = (long long) ceil(log(n+1)/log(10));

    int z[c];
    for (int i=0; i<c; i++) {
        z[c-i-1] = n%10;
        n/=10;
    }

    sort(z,z+c);

    int nb=0,t,s;

    for (int i=0; i < c/2; i++) {
        s = (z[i]+z[c-i-1]);
        t = (s>9) ? 10 : 1;
        nb = (nb*10*t)+s;
    }
    if (c%2) nb=nb*10+z[c/2];


    cout << nb << endl;

    return 0;
}