puncakes

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;


size_t result = -1;

void binarySearch(size_t min, size_t max, size_t target, const vector<size_t>& times){
    while(min <= max){
        size_t mid = min + (max - min) / 2;
        size_t pancakesSorFar = 0;
        for(size_t time : times)
            pancakesSorFar += (mid / time);

        if(pancakesSorFar >= target){
            result = mid;
            max = mid - 1;
        }
        else{
            min = mid + 1;
        }
    }
}

int main() {
    size_t n, k;
    cin >> n >> k;
    size_t maxTime = 0;
    vector<size_t> times(k);
    for(size_t i =0; i < k; i++){
        cin >> times[i];

        if(times[i] > maxTime)
            maxTime = times[i];
    }
    binarySearch(1, n * maxTime, n, times);

    cout << result;
    return 0;
}