#include <bits/stdc++.h>
#pragma GCC optimize("O3")
#define int long long
#define ll long long
#define fi first
#define se second
#define lf ((id<<1))
#define rg ((id<<1)|1)
#define md ((l+r)>>1)
#define pb push_back
using namespace std;
const int MAXN = 1e5+10;
const int INF = 1e9+10;
const int LOG = 20;
int MOD;
typedef pair<int,int> pii;
int sum(int a, int b){ return (a+MOD+b)%MOD; }
void chsum(int &a, int b){ a = sum(a,b); }
int mul(int a, int b){ return (a*b)%MOD; }
int expo(int a, int b){
if(b==0) return 1;
int te = expo(a, b>>1); te = mul(te,te);
return (b%2 ? (a*te)%MOD : te);
}
void chmul(int &a, int b){ a = mul(a,b); }
void chmn(auto &a, auto b){ a = min(a, b); }
void chmx(auto &a, auto b){ a = max(a, b); }
int n, x, a[MAXN], t[MAXN];
int ans;
int p[MAXN], q[MAXN], dp[MAXN];
signed main(){
ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
cin>>x>>n;
for(int i=1; i<=n; i++) cin>>t[i];
for(int i=1; i<=n; i++) cin>>a[i];
vector<pii> vec;
for(int i=1; i<=n; i++){
vec.pb({a[i]-t[i], a[i]+t[i]});
}
sort(vec.begin(), vec.end());
for(int i=1; i<=n; i++){
p[i] = vec[i-1].fi, q[i] = vec[i-1].se;
// cout << p[i] << ' ' << q[i] << " pn\n";
}
int ans = 0;
for(int i=1; i<=n; i++){
int mx = 0;
for(int j=1; j<=i-1; j++){
if(p[j]<p[i] && q[j] < q[i])
chmx(mx, dp[j]);
}
dp[i] = mx+1;
chmx(ans, dp[i]);
// cout << i << ' ' << dp[i] << " dp\n";
}
cout << ans << '\n';
}
