#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define MAXN 30000010
#define V 30000000
inline ll read(){
    ll f = 1, num = 0;
    char c = getchar();
    while(c < '0' || c > '9'){
        if(c=='-') f = -1;c = getchar();
     }
    while(c>='0'&&c<='9') num = num * 10 + c - '0', c = getchar();
    return num * f;
}
int col[MAXN];
int ed[20];
int a[20],n,k;

int nxt(int id, int pos){
    if(pos % a[id] == 0)return ((pos / a[id]) + 1) * a[id] + 1;
    else return pos + 1;
}

bool insert(int id, int lim){
    for(ed[id];ed[id] <= lim; ed[id] = nxt(id, ed[id])){
        if(!col[ed[id]]){
            col[ed[id]] = id;
            ed[id] = nxt(id, ed[id]);
            return true;
        }else{
            if(insert(col[ed[id]], lim)){
                col[ed[id]] = id;
                ed[id] = nxt(id, ed[id]);
                return true;
            }
        }
    }
    return false;
}

bool solve(ll lim){
    for(int i = 1;i <= lim; ++i)col[i] = 0;
    for(int i = 1;i <= n; ++i){
        ed[i] = 1;
        for(int j = 1;j <= k; ++j)if(!insert(i, lim))return false;
    }
    return true;
}

int main(){
    freopen("friends.in", "r", stdin);
    freopen("friends.out", "w", stdout);
    n = read(),k = read();
    for(int i = 1;i <= n; ++i)a[i] = read();
    ll l = 1, r = V;
    while(r > l){
        ll mid = (l + r) >> 1;
        // cout << l << " " << r << endl;
        if(solve(mid))r = mid;
        else l = mid + 1;
    }
    cout << l;
    return 0;
}