// UUID: a70b49d6-ca50-456f-aee5-0cb04d544fb0
#pragma GCC optimize("O3,no-stack-protector")
#include <bits/stdc++.h>
using namespace std;

int n, k;
vector<int> numLess;
vector<vector<int>> nbrs;

int calcLess(int Indx){
    if(0<=numLess[Indx]) return numLess[Indx];
    int ans=0;
    for(int x : nbrs[Indx]) ans=max(ans, calcLess(x)+1);
    return numLess[Indx]=ans;
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cin >> n >> k;
    vector<long long> sortedArr(n+k);
    vector<int> h(n+1), towerH(k);
    for(int i=0;i<n;i++){
        cin >> h[i];
        sortedArr[i]=(((long long)(h[i])<<32)|i);
    }
    for(int i=0;i<k;i++){
        cin >> towerH[i];
        sortedArr[n+i]=(((long long)(towerH[i])<<32)|n+i);
    }
    h[n]=INT_MAX;
    sort(sortedArr.begin(), sortedArr.end());
    stack<int> stc;
    stc.push(n);
    nbrs.resize(n+1);
    for(int i=0;i<n;i++){
        while(h[stc.top()]<h[i]) stc.pop();
        nbrs[stc.top()].push_back(i);
        stc.push(i);
    }
    numLess.resize(n+1, -1);
    calcLess(n);
    
}