#ifndef LOCAL
#include "gap.h"
#endif
#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
long long t, n;
vector<long long> vcL;
void MinMax(long long a, long long b, long long &mn, long long &mx) {
cout << "MinMax(" << a << ", " << b << "): ";
bool MN = false, MX = false;
for (int i = 0; i < n; ++i) {
if (!MN and vcL[i] >= a) {
mn = vcL[i];
MN = true;
}
if (!MX and vcL[n - i - 1] <= b) {
mx = vcL[n - i - 1];
MX = true;
}
if (MN and MX) {
break;
}
}
cout << "mn = " << mn << ", mx = " << mx << '\n';
return;
}
#endif
long long findGap1(int N)
{
vector<long long> num(N, -1);
long long mn = -1, mx = (long long)1E18 + 2;
for (int i = 0; i < (N+1)/2; ++i) {
#ifdef LOCAL
MinMax(mn + 1, mx - 1, mn, mx);
#else
MinMax(mn + 1, mx - 1, &mn, &mx);
#endif
num[i] = mn;
num[N - i - 1] = mx;
if (mn == -1 and mx == -1) assert(false);
else if (mn == mx) break;
}
long long answer = 0;
for (int i = 1; i < N; ++i) {
answer = max(answer, num[i] - num[i - 1]);
}
return answer;
}
long long findGap2(int N)
{
vector<long long> num(N, -1);
long long magic[] = {-1, (long long)1E9, (long long)1E16};
long long mn = magic[rand() % 3], mx = (long long)1E18 + 1;
for (int i = 0; i < 40000; ++i) {
#ifdef LOCAL
MinMax(mn + 1, mx - 1, mn, mx);
#else
MinMax(mn + 1, mx - 1, &mn, &mx);
#endif
num[i] = mn;
num[N - i - 1] = mx;
if (mn == -1 and mx == -1) assert(false);
else if (mn == mx) break;
}
long long answer = 0;
for (int i = 1; i < 40000; ++i) {
answer = max(answer, num[i] - num[i - 1]);
}
for (int i = N-39999; i < N; ++i) {
answer = max(answer, num[i] - num[i - 1]);
}
return answer;
}
long long findGap(int T, int N) {
if (T == 1 or N <= 80000) return findGap1(N);
else return findGap2(N);
}
#ifdef LOCAL
int main() {
long long ANSWER = 0;
cin >> t >> n;
vcL.assign(n, 0);
for (int i = 0; i < n; ++i) {
cin >> vcL[i];
if (i) ANSWER = max(ANSWER, vcL[i] - vcL[i - 1]);
}
long long myAns = findGap(t, n);
cout << "Your answer: " << myAns << '\n';
cout << "Real answer: " << ANSWER << '\n';
return 0;
}
#endif
