#include "bits/stdc++.h"
using namespace std;
typedef long long ll;

int mod(const string &num, int a){
    ll ret=0;

    for(int i=0;i<(int)num.length();i++)
        ret=(ret*10+(int)(num[i]-'0'))%a;

    return ret;
}

string addBigNumbers(string number1, string number2) {
    if (number1.length() > number2.length())
        swap(number1, number2);
    string sum = "";
    int len1 = number1.length();
    int len2 = number2.length();
    int digitDiff = len2 - len1;
    int carry = 0;
    int intSum;
    for (int i=len1-1; i>=0; i--) {
        intSum = ((number1[i]-'0') + (number2[i+digitDiff]- '0') + carry);
        sum.push_back(intSum%10 + '0');
        carry = intSum/10;
    }
    for (int i=digitDiff-1; i>=0; i--) {
        intSum = ((number2[i]-'0')+carry);
        sum.push_back(intSum%10 + '0');
        carry = intSum/10;
    }
    if (carry)
        sum.push_back(carry+'0');
    reverse(sum.begin(), sum.end());
    return sum;
}

void solve(){
    string a;
    int b;
    cin>>a>>b;

    int m=mod(a,b);
    if(m) m=b-m;

    cout<<addBigNumbers(a,to_string(m));
}

int main(){
    ios::sync_with_stdio(0);
    cin.tie(0);

    int t;
    cin>>t;

    while(t--){
        solve();
        cout<<'\n';
    }
}