/* Author haleyk10198 */
/* 作者:  haleyk10198 */
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define MOD 1000000007
#define LINF (1LL<<60)
#define INF 2147483647
#define PI 3.1415926535897932384626433
#define ll long long
#define pii pair<int,int>
#define mp(x,y) make_pair((x),(y))

using namespace std;
using namespace __gnu_pbds;

string itos(int x){
	stringstream ss;
	ss<<x;
	return ss.str();
}

//GREEDY?! NOT DP?! NO WAY, JUST WAITING FOR PRESTEST KO.
//OK FFS IF I GOT SLAMMED DOWN CUZ FORGOT TO HANDLE <0 ... I... I...

//OH GOSH EXCEPTIONS EXCEPTIONS EXCEPTIONS

int len,n,p,t,cur,res,mx;

map<int,int> dp;

int main(){
	//freopen("input.txt","r",stdin);
	//freopen("output.txt","w",stdout);
	ios_base::sync_with_stdio(false);
	cin>>len>>n>>p>>t;
	dp[0]=0;
	for(int i=0,l,r;i<n;i++){
		cin>>l>>r;
		cur=dp.rbegin()->first;
		int tmp=dp[cur];
		cur=max(l,cur);
		tmp+=(r-cur)/p;
		cur=r-(r-cur)%p;
		if(--dp.upper_bound(cur+t)->second<tmp)
			dp[cur+t]=tmp;
		if(l-t<0)
			tmp=0;
		else
			tmp=--dp.upper_bound(l-t)->second;
		r-=(r-l)%p;
		tmp+=(r-l)/p;
		if((--dp.upper_bound(r+t))->second<tmp)
			dp[r+t]=tmp;
	}
	cout<<(dp.rbegin()->second)<<endl;
	return 0;
}