#include <iostream>

using namespace std;

int main() {
    int n;
    cin >> n;
    if(n<=0) {
        cout << "-1" << endl;
        return -1;
    }

    // 1234
    int result = 0;
    int incrementer = 1;
    do {
        int c = n%10;
        if(c%2==0) result += (c/2*incrementer);
        else result += (c*incrementer);

        n /= 10;
        incrementer *= 10;
    } while(n!=0);

    cout << result << endl;
}