#include<iostream>
using namespace std;
int main() {
    int t;
    cin>>t;
    while(t--){
 
        int n1,n2,a,b;
        int k=0;
        cin>>n1>>n2;
        int p[105];
        while(n1>0&&n2>0){
             a=n1%5;
             b=n2&5;
             n1=n1/10;
             n2=n2/10;
            if(a==b){
                p[k]=0;
                k++;
            }
            else{
 
            p[k]=1;
 
            k++;
            }
        }
 
        for(int i=k-1;i>=0;i--){
            cout<<p[i];
        }
    }
	return 0;
}

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