long?long

#include <bits/stdc++.h>

using namespace std;

const int N = 300;

bool lesen (int left[], int right[]) {
    int check[N];
    for (int i = 0; i < N; ++i) {
        check[i] = left[i];
    }
    for (int i = N - 1; i >= 0; --i) {
        if (check[i] < 99) {
            check[i] += 1;
            break;
        }
        else {
            check[i] = 0;
        }
    }
    for (int i = 0; i < N; ++i) {
        if (right[i] > check[i]) {
            return true;
        }
        else if (right[i] < check[i]) {
            return false;
        }
        else {

        }
    }
    return false;
}

void get_mid(int left[], int right[], int mid[]) {
    for (int i = 0; i < N; ++i) {
        mid[i] = 0;
    }
    int dot = 0;
    for (int i = N - 1; i >= 0; --i) {
        mid[i] = (right[i] + left[i] + dot) % 100;
        dot = (right[i] + left[i] + dot) / 100;
    }
    for (int i = 0; i < N; ++i) {
        if (i != N - 1)
            mid[i + 1] += 100 * (mid[i] % 2);
        mid[i] = mid[i] / 2;
    }
}

int main()
{
    //for (int first = 2; first < 1000; ++first) {
    //    for (int second = 2; second < first; ++second) {

    string a;
    cin >> a;

    //vector <char> al = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};

    //int t = first, k = second;

    /*while (t > 0) {
        a += al[t % 10];
        t /= 10;
    }
    reverse(a.begin(), a.end());

    while (k > 0) {
        b += al[k % 10];
        k /= 10;
    }
    reverse(b.begin(), b.end());

    //cout << first / second << " ";*/

    int left[N];
    int right[N];
    int mid[N];
    int cur[2 * N];
    int ans[2 * N];

    int f[2 * N];

    for (int i = 0; i < 2 * N; ++i) {
        f[i] = 0;
    }

    if ((int)a.size() % 2 == 1) {
        f[2 * N - (int)a.size() / 2 - 1] = (int) (a[0] - '0');
        for (int i = (int)a.size() - 1; i >= 2; i -= 2) {
            f[2 * N - (int)a.size() / 2 + i / 2 - 1] = ((int)(a[i - 1] - '0') * 10 + (int)(a[i] - '0'));
        }
    }
    else {
        for (int i = (int)a.size() - 1; i >= 1; i -= 2) {
            f[2 * N - (int)a.size() / 2 + i / 2] = ((int)(a[i - 1] - '0') * 10 + (int)(a[i] - '0'));
        }
    }

    int st = 0;

    while (f[st] == 0 && st < 2 * N) {
        st += 1;
    }

    if (st == 2 * N) {
        cout << 0;
        return 0;
    }

    for (int i = 0 ; i < N; ++i) {
        left[i] = 0;
        right[i] = f[N + i];
    }

    left[N - 1] = 1;

    while (lesen(left, right)) {
        for (int i = 0; i < N; ++i) {
            mid[i] = 0;
        }
        get_mid(left, right, mid);
        for (int i = 0; i < 2 * N; ++i) {
            ans[i] = 0;
        }
        for (int i = N - 1; i >= 0; --i) {
            for (int j = 0; j < 2 * N; ++j) {
                cur[j] = 0;
            }
            int pr = mid[i]; int dot = 0;
            if (pr == 0) {
                continue;
            }
            for (int j = N - 1; j >= 0; --j) {
                cur[2 * N - 1 - (N - 1 - i) - (N - 1 - j)] = (mid[j] * pr + dot) % 100;
                dot = (mid[j] * pr + dot) / 100;
            }
            dot = 0;
            for (int j = 2 * N - 1; j >= 0; --j) {
                int x = (ans[j] + cur[j] + dot) / 100;
                ans[j] = (ans[j] + cur[j] + dot) % 100;
                dot = x;
            }
        }
        bool great = false;
        for (int i = 0; i < 2 * N; ++i) {
            if (ans[i] > f[i]) {
                great = true;
                break;
            }
            else if (ans[i] < f[i]){
                break;
            }
        }
        if (great) {
            for (int i = 0; i < N; ++i) {
                right[i] = mid[i];
            }
        }
        else {
            for (int i = 0; i < N; ++i) {
                left[i] = mid[i];
            }
        }
    }

    for (int i = 0; i < 2 * N; ++i) {
            ans[i] = 0;
    }
    for (int i = N - 1; i >= 0; --i) {
        for (int j = 0; j < 2 * N; ++j) {
            cur[j] = 0;
        }
        int pr = left[i]; int dot = 0;
        if (pr == 0) {
            continue;
        }
        for (int j = N - 1; j >= 0; --j) {
            cur[2 * N - 1 - (N - 1 - i) - (N - 1 - j)] = (left[j] * pr + dot) % 100;
            dot = (left[j] * pr + dot) / 100;
        }
        dot = 0;
        for (int j = 2 * N - 1; j >= 0; --j) {
            int x = (ans[j] + cur[j] + dot) / 100;
            ans[j] = (ans[j] + cur[j] + dot) % 100;
            dot = x;
        }
    }

    for(int j = 0; j < 2 * N; ++j) {
        if (ans[j] != f[j]) {
            cout << -1 << "\n";
            return 0;
        }
    }

    bool flag = true;

    int anss = 0;

    for (int i = 0; i < N; ++i) {
        if (left[i] == 0 && flag) {
            continue;
        }
        else if (left[i] != 0 && flag) {
            cout << left[i];
            //anss *= 10; anss += left[i];
            flag = false;
        }
        else {
            if (left[i] < 10) {
                cout << 0;
            }
            //anss *= 10; anss += left[i];
            cout << left[i];
        }
    }

    cout << "\n";
    /*if (first / second != anss) {
        cout << first << " " << second << " " << anss << "\n";
    }
    //cout << "\n";

    }
    }*/


    return 0;
}