#include<bits/stdc++.h> using namespace std;

int main() { int n; cin >> n; int l; cin >> l; int ants[n]; for (int i = 0; i < n; i++) { cin >> ants[i]; } int minTime = 0; for (int i = 0; i < n; i++) { int timeToLeftEnd = ants[i]; int timeToRightEnd = l - ants[i]; int currentMinTime = min(timeToLeftEnd, timeToRightEnd); minTime = max(minTime, currentMinTime); } cout << minTime << endl; return 0; } （这都不会）