#include <bits/stdc++.h>

using namespace std;

int axa[100006];
bool check (int k, int t, int G)
{
	for (int i = 1; i<=k+1; ++i)
	{
		int dist = axa[i] - axa[i-1];
		if (dist > G + t) return false;
		t -= max (0, dist - G);
	}
	return true;
}
int main()
{
    ifstream fin ("ghiozdan.in");
    ofstream fout ("ghiozdan.out");
    int put = 24;
    int d, k, t;
    fin >> d >> k >> t;
    axa[0] = 0;
    axa[k+1] = d;
    for (int i = 1; i<=k; ++i)
    	fin >> axa[i];
    int best = 0;
    if (check(k, t, best))
    {
    	fout << best;
    	return 0;
    }
    for (int i = put; i>=0; --i)
    	if (check(k, t, best + (1<<i)) == false)
    		best += (1<<i);
    fout << best + 1;
    return 0;
}