#include <bits/stdc++.h>

using namespace std;

constexpr int INF = 1e9;

void solve() {
    int t, n; cin >> t >> n;
    vector<int> v(n);
    for(int i=0; i<n; ++i) {
        int a, b; cin >> a >> b;
        v[i] = b - a;
    }
    vector<vector<int>> dp(n, vector<int>(t + 1, INF));
    dp[0][v[0]] = v[0];
    dp[0][0] = v[0];
    for(int i=0; i<n - 1; ++i) {
        for(int j=0; j<=t; ++j) {
            if(dp[i][j] == INF) {
                continue;
            }
            int len = dp[i][j];
            int r = j + v[i + 1];
            if(r <= t) {
                dp[i + 1][r] = min(dp[i + 1][r], max(r, len));
            }
            if(j < v[i + 1] && v[i + 1] + len - j <= t) {
                dp[i + 1][0] = min(dp[i + 1][0], v[i + 1] + len - j);
            } else {
                int l = j - v[i + 1];
                dp[i + 1][l] = min(dp[i + 1][l], len);
            }
        }
    }
    int mn = INF;
    for(int j=0; j<=t; ++j) {
        mn = min(mn, dp[n - 1][j]);
    }
    if(mn > t) {
        cout << "impossible\n";
        exit(0);
    }
}

int main() {
    int f; cin >> f;
    for(int i=0; i<f; ++i) {
        solve();
    }
    cout << "possible\n";
}