#include <iostream>
#include <vector>
#include <algorithm>
#include <set>
#include <map>
#include <numeric>
#include <queue>
#include <deque>
#include <list>
#include <stack>
#include <deque>
#include <cmath>
#include <complex>
#include <cassert>
#include <cstring>
#include <functional>
#include <bitset>
#include <climits>

using namespace std;
typedef  long long ll;
typedef pair<int,int> PII;
typedef vector<int> VI;
typedef vector<VI> VVI;
#define  MP make_pair
#define  PB push_back
#define inf  (1LL << 60)
#define rep(i,n) for(int i=0;i<(int)(n);++i)
#define cmn(x,y) x=min(x,y)
template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    std::fill( (T*)array, (T*)(array+N), val );
}
template<typename T> class segtree {
private:
    int n,sz;
    vector<pair<T, int> > node;
public:
    segtree(vector<T>& v){
        sz = (int)v.size();
        n = 1;
        while(n < sz){
            n *= 2;
        }
        node.resize(2*n);
        rep(i,sz){
            node[i+n] = make_pair(v[i], i);
        }
        for(int i=n-1; i>=1; i--){
            node[i] = min(node[2*i], node[2*i+1]);
        }
    }
    void update(int k, T a)
    {
    	node[k+=n] = make_pair(a, k);
    	while(k>>=1){
            node[k] = min(node[2*k], node[2*k+1]);
    	}
    }
    pair<T, int> query(int a,int b,int k=0,int l=0,int r=-1)
    {
        pair<T, int> res1 = make_pair(inf, -1);
        pair<T, int> res2 = make_pair(inf, -1);
        a += n, b += n;
        while(a != b){
            if(a % 2) cmn(res1, node[a++]);
            if(b % 2) cmn(res2, node[--b]);
            a >>= 1, b>>= 1;
        }
        return min(res1, res2);
    }
    void print()
    {
        rep(i,sz){
            pair<T, int> p;
            p = query(i,i+1);
            cout << "st[" << i << "]: " << p.first << " " << p.second << endl;
        }
    }
};


int n;
ll d;
ll saiki(segtree<ll>& sg, int a,int b){
    //cerr << a << " " << b << endl;
    if(b==a+1)return 0;
    auto p = sg.query(a,b);
    ll s = p.first;
    ll ans = 0;
    int ind = p.second;
    if(ind-1>=a){
        ll xx = sg.query(ind-1,ind).first;
        ans += s+d+xx;
        sg.update(ind-1,min(xx,s+d));
        ans += saiki(sg,a,ind);
    }
    if(ind+1<b){
        ll xx = sg.query(ind+1,ind+2).first;
        ans += s+d+xx;
        sg.update(ind+1,min(xx,s+d));
        ans += saiki(sg,ind+1,b);
    }
    return ans;
}


int main(){
    cin >> n >> d;
    vector<ll>v(n+1);
    rep(i,n)cin >> v[i];
    segtree<ll> sg(v);
    ll ans = saiki(sg,0,n);
    cout << ans << endl;
    return 0;
}

#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<string.h>

#ifdef LOCAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
#else
#define NDEBUG
#define eprintf(...) do {} while (0)
#endif
#include<cassert>

using namespace std;

typedef long long LL;
typedef vector<int> VI;

#define REP(i,n) for(int i=0, i##_len=(n); i<i##_len; ++i)
#define EACH(i,c) for(__typeof((c).begin()) i=(c).begin(),i##_end=(c).end();i!=i##_end;++i)

template<class T> inline void amin(T &x, const T &y) { if (y<x) x=y; }
template<class T> inline void amax(T &x, const T &y) { if (x<y) x=y; }
template<class Iter> void rprintf(const char *fmt, Iter begin, Iter end) {
    for (bool sp=0; begin!=end; ++begin) { if (sp) putchar(' '); else sp = true; printf(fmt, *begin); }
    putchar('\n');
}

int N;

struct Data {
    int h, p;
    bool operator<(const Data &o) const {
	return min(h, o.h-p) > min(o.h, h-o.p);
    }
} D[5011];

LL X[5011];

void MAIN() {
    scanf("%d", &N);
    REP (i, N) scanf("%d%d", &D[i].h, &D[i].p);
    sort(D, D+N);

    memset(X, 0x3f, sizeof X);
    LL INF = X[0];
    X[0] = 0;
    REP (i, N) {
	for (int j=i; j>=0; j--) {
	    if (X[j] <= D[i].h) {
		amin(X[j+1], X[j] + D[i].p);
	    }
	}
    }
    int ans = 0;
    REP (i, N+1) if (X[i] < INF) ans = i;
    printf("%d\n", ans);
}

int main() {
    int TC = 1;
//    scanf("%d", &TC);
    REP (tc, TC) MAIN();
    return 0;
}

