#include <bits/stdc++.h>
using namespace std;
char a[10000],b[10000];
int a1[10000],b1[10000],lena,lenb,res[10000],lenres;
int main(){
	cin >> a >> b;
	lena = strlen(a);
	lenb = strlen(b);
	for (int i=0; i<=lena-1; i++){
		a1[lena-i-1] = a[i]-'0';
	}
	for (int i=0; i<=lenb-1; i++){
		b1[lenb-i-1] = b[i]-'0';	
	}
	lenres = max(lena,lenb);
	for (int i=0; i<lenres; i++){	
		if (a1[i]-b1[i] < 0){
			a[i] += 10;
			a[i+1]--;
		}
		res[i]=a1[i]-b1[i];
	}
	while (res[lenres-1]==0 && lenres>1){
		lenres--;
	}
	for (int i=lenres-1; i>=0; i--){
		cout << res[i];
	}
	return 0;
}