#include<iostream>
using namespace std;

void citire(int a[1000], int &n)
{
	char cif;
	int i;
	cin>>n;
	for(i=n;i>=1;i--)
		{ cin>>cif;
	      a[i]=cif-48;//transform sin cifra in numar (cifa este caracter)
		} 
}

int maimare(int a[1000], int n, int b[1000], int m)
{
	int i;
	if(n>=m) return 1;
		else if(n<m) return 0;
	         else
			 { 
				 i=m;
				 while(a[i]==b[i]) i--;
				 if(a[i]>=b[i]) return 1;
                 else return 0;				 
			 }				 
}

int main()
{
	int a[1000],b[1000],s[1000],n,m,p,i,k,semn,aux;
	citire(a,n);
	citire(b,m);
	if(maimare(a,n,b,m)==0)
	{//b>a
		p=m;
	    for(i=n+1;i<=m;i++) a[i]=0;
	    for(i=1;i<=p;i++) s[i]=b[i]; //pun pe b in s
		semn=-1;
		for(i=1;i<=p;i++) b[i]=a[i];// pun pe a in b;
	}
	else //a>b
	{	p=n;
		for(i=m+1;i<=n;i++) b[i]=0;
		for(i=1;i<=p;i++) s[i]=a[i]; //pun pe a in s;
	}
	for(i=1;i<=p;i++)
	{
		if(s[i]>=b[i]) s[i]=s[i]-b[i];
		else
		{ //ma imprumut
			k=i+1;
			while(s[k]==0) { s[k]=9; k++;}
			s[k]--;
			s[i]=10+s[i]-b[i];
		}
	}
	if(semn==-1) cout<<"-";
	while(s[p]==0) p--;
	for(i=p;i>=1;i--) cout<<s[i];
	return 0;
}