#include<cstdio>
#include<cstring>
#include<cmath>
#include<ctime>
#include<string>
#include<vector>
#include<queue>
#include<deque>
#include<set>
#include<list>
#include<stack>
#include<bitset>
#include<algorithm>
#define INF (1 << 30)
#define pb push_back
#define mkp make_pair
#define pii pair<int, int>
#define ll long long
#define nxt (*it)
#define type int
#define FOR(i,a,b)\
   for(int i=a; i<=b; ++i)
#define FORR(i,a,b)\
   for(int i=a; i>=b; --i)
#define ALLR(g) \
   for(typeof(g.rbegin()) it=g.rbegin(); it!=g.rend(); ++it)
#define ALL(g)\
   for(typeof(g.begin()) it=g.begin(); it!=g.end(); ++it)
#define infile "tricouri.in"
#define outfile "tricouri.out"
using namespace std;

const int K = 5;
const int P = 20;

int DP[K+1][P+1];

int N, Q;


int main(){
    freopen(infile, "r", stdin);
    freopen(outfile, "w", stdout);

    scanf("%d %d", &N, &Q);

    int t;
    FOR(idx,1,N){
        scanf("%d", &t);

        FORR(i, min(idx-1, K-1), 0)
           FOR(j,2,P){
               if(!DP[i][j] && i > 0)
                  continue;

               int nrt = DP[i][j] + t;
               FOR(k, 2, P)
                  if(nrt % k == 0 && DP[i+1][k] < nrt)
                     DP[i+1][k] = nrt;
           }
    }

    int k, p;
    while(Q--){
        scanf("%d %d", &k, &p);

        if(!DP[k][p])
           printf("-1\n");
        else
           printf("%d\n", DP[k][p]);
    }

    fclose(stdin);
    fclose(stdout);

    return 0;
}