#include <bits/stdc++.h>   using namespace std;   int n, m;   vector<pair<int, int>> flowers;   vector<int> first_flowers;   vector<long long> pref_sum;   long long answer;   void In() {     flowers.clear();     pref_sum.clear();     first_flowers.clear();     answer = LLONG_MIN;     cin >> n >> m;     flowers.resize(m);     for (int i = 0; i < m; i++) cin >> flowers[i].first >> flowers[i].second;   }   long long GetPrefSum(int start_index) {     return pref_sum.back() -            ((start_index - 1 >= 0) ? pref_sum[start_index - 1] : 0);   }   void Try(int index) {     auto range = equal_range(first_flowers.begin(), first_flowers.end(),                              flowers[index].second);     int less_or_equal = range.second - first_flowers.begin();     int remaining = m - less_or_equal;     remaining = min(remaining, n);     int start_index = m - remaining;     if (index >= start_index) {       long long result = GetPrefSum(start_index);       long long left_take = n - remaining;       result += left_take * flowers[index].second;       answer = max(answer, result);     } else {       long long result = flowers[index].first;       int really_remaining = m - less_or_equal;       really_remaining = min(really_remaining, n - 1);       start_index = m - really_remaining;       result += GetPrefSum(start_index);       long long left_take = n - 1 - really_remaining;       result += left_take * flowers[index].second;       answer = max(answer, result);     }   }   void Solve() {     sort(flowers.begin(), flowers.end());     pref_sum.resize(m);     pref_sum[0] = flowers[0].first;     for (int i = 1; i < m; i++) pref_sum[i] = flowers[i].first + pref_sum[i - 1];     first_flowers.resize(m);     for (int i = 0; i < m; i++) first_flowers[i] = flowers[i].first;     for (int i = 0; i < m; i++) Try(i);   }   void Out() { cout << answer <<   n ; }   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     int t = 1;     cin >> t;     while (t--) {       In();       Solve();       Out();     }   }   