#include<bits/stdc++.h>
using namespace std;
////////// 	Template structure for debugging
#define tr(...) trace(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void trace(const char* name, Arg1&& arg1){
cout << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void trace(const char* names, Arg1&& arg1, Args&&... args){
const char* comma = strchr(names + 1, ',');
cout.write(names, comma-names) << " : " << arg1 << " | " ;
trace(comma+1, args...);
}
#define print(...) pr(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void pr(const char* name, Arg1&& arg1){
cout << arg1 << endl;
}
template <typename Arg1, typename... Args>
void pr(const char* names, Arg1&& arg1, Args&&... args){
const char* comma = strchr(names + 1, ',');
cout << arg1 << " ";
pr(comma+1, args...);
}

void printV(vector<int> &arr)
{
	cout << "Vector : ";
	for(int i=0;i<arr.size();i++)
		cout << arr[i] << " \n"[ i == arr.size()-1 ];
}
void printA(int arr[], int n)
{
	cout << "Array : ";
	for(int i=0;i<n;i++)
		cout << arr[i] << " \n"[ i == n-1 ];
}
//-----------Prime factorization of a number N
	//vector<int> factorize(int N){
		//for(ll i=2; i*i <=N; i++){
		//if(N % i)continue;
		//factors.push_back(i);
		//while(N % i == 0)N /= i;
		//}
		//if(N > 1)factors.push_back(q1);

		//return factors
	//}
//-----------Power for a ^ b
	//int power(int a, int b){
		//int ans = 1;
		//while(b){
		 //if(b&a)ans *= a;
		 //a *= a;
		 //b >>= 1;
		//}
		//return ans
	//}
//-----------factorial of a number n
//int fact(int n){
	//int ans = 1;
	//for(int i=1; i<=n; i++)ans = 1ll * ans * i % MOD;
	//return ans;
//}
//-----------N C r
//int ncr(int n, int r){
	//if(r > n)return 0;
	//if(r==0 || n==0)return 1;
	//if(r==1)return n;
	//int a = fact(n), b = 1ll * fact(n-r) % MOD, c = 1ll * fact(r) % MOD;
	//int ans = 1ll * a * power(b, MOD-2) % MOD;
	//ans = 1ll * ans * power(c, MOD-2) % MOD;
	//return ans;
//}
//------------------sieve of Eratosthenes
//
//arr[0] = 1;
//arr[1] = 1;
//for(int i=2; i*i <= N; i++){
	//if(!arr[i]){
		//for(int j=i*i; j<=N; j++)
			//arr[j] = 1;
	//}
//}

typedef long long ll;

bool possible(ll num, ll s, ll moves){
	string s1 = to_string(num), s2 = to_string(num + moves);

	if(s2.length() > s1.length())return true;
	int sum1 = 0, sum2 = 0;
	for(int i=0; i<s1.length(); i++)sum1 += s1[i] - '0';

	for(int i=0; i<s1.length(); i++){
		if(s1[i] == s2[i]){
			sum2 += s1[i] - '0';
		}
		else {
			sum2 += s1[i] - '0' + 1;
			break;
		}
	}
	return min(sum1, sum2) <= s;
}

vector<int> arr;
int main(){
	ios_base::sync_with_stdio(0);
    cin.tie(0);
	int t;
	cin >> t;
	while(t--){
		ll num, s;
		cin >> num >> s;
		ll l = 0, r = 1e18+1, m;
		while(l<r){
			m = l + (r-l)/2;
			if(possible(num, s, m))r=m;
			else l = m+1;
		}
		cout << l << endl;
	}

}