#include <bits/stdc++.h>
#ifndef LOCAL
#include "gap.h"
#else
void MinMax(long long, long long, long long*, long long*);
static void my_assert(int k){ if (!k) exit(1); }
long long findGap(int, int);
static int subtask_num, __N;
static long long A[100001];
static long long call_count;
void MinMax(long long s, long long t, long long *mn, long long *mx) {
int lo = 1, hi = __N, left = __N+1, right = 0;
my_assert(s <= t && mn != NULL && mx != NULL);
while (lo <= hi){
int mid = (lo+hi)>>1;
if (A[mid] >= s) hi = mid - 1, left = mid;
else lo = mid + 1;
}
lo = 1, hi = __N;
while (lo <= hi){
int mid = (lo+hi)>>1;
if (A[mid] <= t) lo = mid + 1, right = mid;
else hi = mid - 1;
}
if (left > right) *mn = *mx = -1;
else{
*mn = A[left];
*mx = A[right];
}
if (subtask_num == 1) call_count++;
else if (subtask_num == 2) call_count += right-left+2;
}
int main()
{
FILE *in = stdin, *out = stdout;
my_assert(2 == fscanf(in, "%d%d", &subtask_num, &__N));
my_assert(1 <= subtask_num && subtask_num <= 2);
my_assert(2 <= __N && __N <= 100000);
for (int i=1;i<=__N;i++) my_assert(1 == fscanf(in, "%lld", A+i));
for (int i=1;i<__N;i++) my_assert(A[i] < A[i+1]);
fprintf(out, "%lld\n", findGap(subtask_num, __N));
fprintf(out, "%lld\n", call_count);
}
#endif
#ifdef LOCAL
#include "template\debug.hpp"
#else
#define dbg(...) ;
#define timer(...) ;
#endif
struct Subtask1 {
int n;
Subtask1(int _n) : n(_n) {}
long long solve() {
std::vector<long long> a(n);
MinMax(0, 1e18, &a[0], &a.back());
for (int i = 1; i <= n - i - 1; i++) {
MinMax(a[i - 1] + 1, a[n - i] - 1, &a[i], &a[n - i - 1]);
}
long long ans = a[1] - a[0];
for (int i = 1; i + 1 < n; i++) {
ans = std::max(ans, a[i + 1] - a[i]);
}
return ans;
}
};
struct Subtask2 {
int n;
Subtask2(int _n) : n(_n) {}
long long solve() {
long long lo, hi;
MinMax(0, 1e18, &lo, &hi);
dbg(lo, hi);
// we can do this
long long gap = (hi - lo - 1) / (n - 1);
if (gap * (n - 1) < (hi - lo - 1)) gap++;
dbg(gap);
// we can do that now
long long ans = 0;
for (int i = 0; i < n - 1; i++) {
long long ff = lo + 1 + gap * i;
long long ee = lo + gap * (i + 1);
ee = std::min(ee, hi - 1);
dbg(ff, ee);
long long r1, r2;
MinMax(ff, ee, &r1, &r2);
ans = std::max(ans, r2 - r1);
if (i == 0) {
ans = std::max(ans, r1 - lo);
}
if (i == n - 2) {
ans = std::max(ans, hi - r2);
}
}
return ans;
}
};
long long findGap(int T, int N) {
dbg("called ", T, N);
if (T == 1) {
Subtask1 sub1(N);
return sub1.solve();
} else {
Subtask2 sub2(N);
return sub2.solve();
}
}
