#include <bits/stdc++.h>
using namespace std;
int main()
{
	int a[501],b[501],c[502];
	string s1,s2;
	cin>>s1>>s2;
	if (s1.size()<s2.size()||(s1.size()==s2.size()&&s1<s2))
	{
		swap (s1,s2),cout<<"-";
	}
	a[0]=s1.size();
	for (int i=1;i<a[0];i++)
	{
		a[i]=s1[a[0]-i]-47;
	}
	b[0]=s2.size();
	for (int i=1;i<b[0];i++)
	{
		b[i]=s2[b[0]-i]-47;
	}
	int i=1;
	while (i<=a[0]||i<=b[0])
	{
		if (a[i]<b[i])
		{
			a[i]+=10;
			a[i+1]--;
		}
		c[i]=a[i]-b[i];
		i++;
	}
	for (int j=i;j>=i;j--)
	{
		cout<<c[j];
	}
	return 0;
}