#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
int a[201],b[201];
char c[201];
int main(){
gets(c);
int lena = strlen(c);
for(int i=0;i<lena;i++)
a[i] = c[i] - '0';
reverse(a,a+lena);
gets(c);
int lenb = strlen(c);
for(int i=0;i<lenb;i++)
b[i] = c[i] - '0';
reverse(b,b+lenb);
for(int i=0;i<lenb;i++){
if(a[i]<b[i]){
a[i] = a[i] + 10 - b[i];
a[i+1] = a[i+1] -1;
}else{
a[i] = a[i] - b[i];
}
}
reverse(a,a+lena);
int i=0;
while(a[i]==0) i++;
for(;i<lena;i++)
cout << a[i];
cout << endl;
return 0;
}