#include<bits/stdc++.h>
using namespace std;
string s1,s2;
int a[250],b[250],c[250];
int main(){
    cin>>s1>>s2; 
    if(s1.size()<s2.size()||s1.size()==s2.size()&&s1<s2){
    	cout'-';
    	swap(s1,s2);
	}
	for(int i=s1.size()-1;i>=0;i--){
        a[s1.size()-1-i]=s1[i]-48;
    }
     for(int i=s2.size()-1;i>=0;i--){
        b[s2.size()-1-i]=s2[i]-48;
    }
    for(int i=0;i<s1.size();i++){
        if(a[i]<b[i]){
            a[i]=a[i]+10;
            a[i+1]=a[i+1]-1;
        }
        c[i]=a[i]-b[i];
    }
    for(int i=s1.size()-1;i>=0;i--){
        if(c[i]!=0){
            p=i;
            break;
        }
    }
    for(int i=p;i>=0;i--){
        cout<<c[i];
    }
    return 0; 
}

/**************************************************************
	Problem: 1269
	User: linyuhang
	Language: C++
	Result: Compile Error
****************************************************************/