#include <bits/stdc++.h>
using namespace std;

long long int check(map<long long int,long long int> &hm,long long int n,long long int mid){

    long long int workers = 0;
    long long int tasks = 0;

    for(int i=1;i<=n;i++){
        if(hm[i]>mid){
            tasks+=(hm[i]-mid);
        }
        else{
            workers+=((mid-hm[i])/2);
        }
    }
    return workers>=tasks;
}

int minimumDaysForCharity(long long int n,long long int m, vector<long long int> &a){

    map<long long int,long long int > hm;

    for(int i=1;i<=n;i++){
        hm[i] = 0;
    }

    for(int i=0;i<m;i++){
        hm[a[i]]++;
    }

    long long int start =0;
    long long int end = 1e12;
    long long int ans = 0;

    while(start<=end){
        long long int mid = (start+end)/2;

        if(check(hm,n,mid)){
            ans = mid;
            end = mid-1;
        }
        else{
            start = mid+1;
        }
    }
    return ans;
}

signed main() {
    long long int N;
    long long int M;
    cin>>N>>M;

    vector<long long int> S(M);
    for(int i=0;i<M;i++){
        cin>>S[i];
    }
    cout<<minimumDaysForCharity(N,M,S)<<endl;
}