#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <chrono>
#include <climits>
#include <cmath>
#include <cstdio>
#include <deque>
#include <iomanip>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <unordered_map>
#include <unordered_set>
#include <vector>
using namespace std;

template <class T1, class T2>
ostream& operator << (ostream& out, const pair <T1, T2> p)
{
	out << '(' << p.first << ',' << p.second << ')';
	return out;
}

template <class T1, class T2>
istream& operator >> (istream& in, pair<T1, T2> &p)
{
	in >> p.first >> p.second;
	return in;
}

template <class T>
istream& operator >> (istream& in, vector<T> &v)
{
	for (T &x : v)
		in >> x;
	return in;
}

template <class T>
ostream& operator << (ostream& out, const vector<vector<T>> &v)
{
	for (const vector<T> &x : v)
		out << x << '\n';
	return out;
}

template <class T>
ostream& operator << (ostream& out, const vector<T> &v)
{
	for (const T &x : v)
		out << x << ' ';
	return out;
}

long long gcd (long long a, long long b)
{
	if (b > a)
		swap(a, b);
	return (b ? gcd(b, a % b) : a);
}

using ll   = long long;
using pii  = pair<int, int>;
using pll  = pair<long long, long long>;
using tiii = pair<pair<int, int>, int>;
using vi   = vector<int>;
using vl   = vector<long long>;
using vvi  = vector<vector<int>>;
using vvl  = vector<vector<long long>>;

#define F          first
#define S          second
#define First      first.first
#define Second     first.second
#define Third      second
#define mp         make_pair
#define rep(i,a,b) for (int i = (a); i < (b); i++)
#define per(i,b,a) for (int i = (b); i > (a); i--)
#define all(x)     x.begin(), x.end()
#define ret(x)     return cout << x, 0;
#define throwex    throw runtime_error ("Found the error.");

const int h = 1000000007;

signed main()
{
	ios::sync_with_stdio(false);
	#ifdef ONLINE_JUDGE
	cin.tie(nullptr);
	cerr.setstate(ios::failbit);
	#endif

	int n, m, k;
	cin >> n >> m >> k;
	vi L(m), R(m);
	vvi v(n);
	rep(i,0,m)
	{
		cin >> L[i] >> R[i];
		L[i]--, R[i]--;
		rep(j,L[i], R[i]+1)
			v[j].push_back(i);
	}
	int f_ans = 0;
	for(int l = 0, r = k - 1; r < n; l++, r++)
	{
		vi cnt(m);
		rep(i,l,r+1)
		{
			for(int z : v[i])
				cnt[z]++;
		}
		vi c(n);
		rep(i,0,m)
		{
			if(R[i] - cnt[i] >= L[i])
			{
				c[R[i] - cnt[i]] += 1;
				if(max(R[i] - k, L[i] - 1) >= 0)
					c[max(R[i] - k, L[i] - 1)] -= 1;
				
				int z = min(R[i] - L[i] + 1, k) - cnt[i];
				if(L[i] + z + cnt[i] - 1 - k >= 0)
					c[L[i] + z + cnt[i] - 1 - k] -= 1;
				if(L[i] - 1 - k >= 0)
					c[L[i] - 1 - k] += 1;
			}
		}
		int z = 0;
		per(i,n-1,-1)
		{
			z += c[i];
			c[i] = z;
		}
		z = 0;
		per(i,n-1,-1)
		{
			z += c[i];
			c[i] = z;
		}
		int ans = accumulate(all(cnt), 0);
		int f = 0;
		rep(i,l+1,n)
		{
			f = max(f, c[i]);
		}
		ans += f;
		f_ans = max(f_ans, ans);
	}
	cout << f_ans;
}
