#include<bits/stdc++.h>
using namespace std;

const int NMAX = 1000;
int main(int argc,char* argv[]) {

ios_base::sync_with_stdio(false);
cin.tie(NULL);
///
string a,b;
cin >> a >> b;
vector<int> A(NMAX,0),B(NMAX,0),C(NMAX,0),ANS(NMAX,0);
int j = 0;
for(int i = a.size() - 1; i >=0; i--) {
    A[j] = a[i]-'0';
    j++;
}
j = 0;
for(int i = b.size() - 1; i >=0; i--) {
    B[j] = b[i]-'0';
    j++;
}

for(int i = 0; i <= NMAX; i++){
    int f;
    int s = A[i] - B[i] - C[i];
    if(s < 0){
        ANS[i] = A[i] + 10 - B[i] - C[i];
        C[i+1] = 1;
    }
    else ANS[i] = s;
}

int f=NMAX;
while(ANS[f] == 0){
f--;
}
if(f == -1){
    cout << 0;
    return 0;
}
for(int i = f; i >=0; i--) cout << ANS[i];
///
return 0;
}