#include<bits/stdc++.h>
using namespace std;
string a,b;
int s1[10100],s2[10100],sum[10100],num;
int main(){ 
	cin>>a>>b;
	if(b>a)
	    cout<<"-";
	if(a>=b){
		for(int i=0;i<a.length();i++)
		    s1[a.length()-1-i]=a[i]-'0';
	    for(int i=0;i<b.length();i++)
		    s2[b.length()-1-i]=b[i]-'0';
	}else{
		for(int i=0;i<a.length();i++)
		    s2[a.length()-1-i]=a[i]-'0';
	    for(int i=0;i<b.length();i++)
		    s1[b.length()-1-i]=b[i]-'0';
	}
	num=max(a.length(),b.length())-1;
	for(int i=0;i<=num;i++){
		if(s1[i]>=s2[i])
		    sum[i]=s1[i]-s2[i];
		else{
			s1[i+1]--;
			sum[i]=10+s1[i]-s2[i];
		}
	}
	while(num>=1){
		num--;
	}
	for(int i=num;i>=0;i--)
	    cout<<sum[i];
	return 0;
}