#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

vector<int> read()
{
    vector<int> tmp;
    char ch = getchar();
    while (ch <= '9' && ch >= '0')
    {
        tmp.push_back(ch - '0');
        ch = getchar();
    }
    reverse(tmp.begin(), tmp.end());
    return tmp;
}

// vector<int> sol(vector<int> x, vector<int> y)
// {
// }

vector<int> i2vec(int x)
{
    vector<int> res;
    while (x)
    {
        res.push_back(x % 10);
        x /= 10;
    }
    return res;
}

void print(const vector<int> &a)
{
    // for (int i = 0; i < a.size(); ++i)
    for (int i = a.size() - 1; i >= 0; --i)
        cout << a[i];
    cout << "\n";
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    vector<int> a = read();
    vector<int> b = read();
    // int mn = min(a.size(), b.size());
    int mx = max(a.size(), b.size());
    a.resize(mx, 0);
    b.resize(mx, 0);
    // print(a);
    // print(b);

    // vector<int> adda(a.size());
    // vector<int> addb(b.size());

    int i, j;
    j = -1;
    for (i = mx - 1; i >= 0; --i)
    {
        if (a[i] + b[i] >= 10)
        {
            for (j = i + 1; j < mx; ++j)
            {
                if (a[j] + b[j] < 9)
                {
                    j--;
                    break;
                }
            }
            j = min(j, mx - 1);
            break;
        }
    }
    if (j == -1)
    {
        cout << 0 << "\n";
        return 0;
    }
    // cout << "j: " << j << endl;
    vector<int> big = a;
    for (int x = j; x >= 0; --x)
    {
        if (a[x] > b[x])
        {
            break;
        }
        else if (a[x] < b[x])
        {
            big = b;
            break;
        }
    }
    vector<int> ans;

    bool jin = false;
    for (int i = 0; i <= j; ++i)
    {
        if (jin == false)
        {
            if (big[i] == 0)
            {
                ans.push_back(0);
            }
            else
            {
                ans.push_back(10 - big[i]);
                jin = true;
            }
        }
        else
        {
            ans.push_back(9 - big[i]);
        }
    }
    while (ans.size() > 1 && ans[ans.size() - 1] == 0)
    {
        ans.pop_back();
    }
    print(ans);
    // cout << ans << "\n";

    return 0;
}