#include <iostream>
#include <vector>
#include <algorithm>
 
using namespace std;
 
int maxCitiesWithFuel(int N, int M, vector<int>& cityDemand, vector<int>& stationSupply) {
    sort(cityDemand.begin(), cityDemand.end());
    sort(stationSupply.begin(), stationSupply.end());
 
    int cityIdx = 0, stationIdx = 0, count = 0;
 
    while (cityIdx < N && stationIdx < M) {
        if (stationSupply[stationIdx] >= cityDemand[cityIdx]) {
            // Station can fulfill this city's demand
            count++;
            cityIdx++;
            stationIdx++;
        } else {
            // Station cannot fulfill, try next station
            stationIdx++;
        }
    }
 
    return count;
}
 
int main() {
    int N, M;
    cin >> N >> M;
    vector<int> cityDemand(N);
    vector<int> stationSupply(M);
 
    for (int i = 0; i < N; ++i) {
        cin >> cityDemand[i];
    }
 
    for (int i = 0; i < M; ++i) {
        cin >> stationSupply[i];
    }
 
    cout << maxCitiesWithFuel(N, M, cityDemand, stationSupply) << endl;
    return 0;
}
 

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