#include <bits/stdc++.h>
using namespace std;
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int tt;
cin >> tt;
while (tt--) {
int n, m, a, b;
cin >> n >> m >> a >> b;
vector<int> s(m);
for (int i = 0; i < m; i++) {
cin >> s[i];
}
sort(s.begin(), s.end());
int cnt = abs(a - b) - 1;
int total = (a < b ? b - 1 : n - b) - 1;
// cout << total << " " << cnt << " ";
int u = total - cnt;
// cout <<u << endl;
int ans = 0;
for (int i = 0; i < m; i++) {
u = max(u + 1, s[i]);
if (u > total) {
break;
}
ans += 1;
}
cout << ans << '\n';
}
return 0;
}
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