文件目录

#include <bits/stdc++.h>
using namespace std;
string sub(string a, string b)
{
    reverse(a.begin(), a.end());
    reverse(b.begin(), b.end());
    while (b.size() < a.size())
        b.push_back('0');
    for (int i = 0; i < a.size(); i++)
    {
        a[i] = a[i] - b[i] + 48;
        if (a[i] < 48)
        {
            a[i] += 10;
            a[i + 1]--;
        }
    }
    while (a.back() == '0')
        a.pop_back();
    reverse(a.begin(), a.end());
    return a.empty() ? "0" : a;
}
int main()
{
    string a, b;
    cin >> a >> b;
    cout << sub(a, b);
    return 0;
}