#include<iostream>
#include<string>
using namespace std;
int main() {
	string s1, s2;
	int a1[10100] = { 0 }, a2[10100] = { 0 }, a3[10100] = { 0 };
	getline(cin, s1);
	getline(cin, s2);
	for (int i = 0; i < s1.size(); i++)
	{
		a1[s1.size() - i - 1] = s1[i] - '0';
	}
	for (int i = 0; i < s2.size(); i++)
	{
		a2[s2.size() - i - 1] = s2[i] - '0';
	}
	int len = s1.size();
	if (s1.size() < s2.size())len = s2.size();
	for (int i = 0; i < len; i++)
	{
		a3[i] = a1[i] - a2[i];
	}
	for (int i = 0; i < len; i++)
	{
		if (a3[i] < 0)
		{
			a3[i] += 10;
			a3[i + 1]--;
		}
	}
	if (a3[len] < 0)
	{
		for (int i = 1; i < len; i++)
		{
			a3[i] = 10 - a3[i] - 1;
		}
		a3[0] = 10 - a3[0];
		a3[len - 1] = -a3[len - 1];
	}
	for (int i = len-1; i >= 0; i--)
	{
		cout << a3[i];
	}

}