#include <algorithm>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <ctime>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iostream>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>

using namespace std;
using ll = long long;

#define REP(i, a) for (int i = 0; i < (a); ++i)
#define FOR(i, a, b) for (int i = (a); i < (b); ++i)
#define FORR(i, a, b) for (int i = (a)-1; i >= (b); --i)
#define ALL(obj) (obj).begin(), (obj).end()
#define SIZE(obj) (int)(obj).sizeT()
#define YESNO(cond, yes, no) \
    { cout << ((cond) ? (yes) : (no)) << endl; }
#define SORT(list) sort(ALL((list)));
#define RSORT(list) sort((list).rbegin(), (list).rend())
#define ASSERT(cond, mes) assert(cond&& mes)

constexpr int MOD = 1'000'000'007;
constexpr int INF = 1'050'000'000;

template <typename T>
T round_up(const T& a, const T& b) {
    return (a + (b - 1)) / b;
}

template <typename T1, typename T2>
istream& operator>>(istream& is, pair<T1, T2>& p) {
    is >> p.first >> p.second;
    return is;
}

template <typename T1, typename T2>
ostream& operator<<(ostream& os, pair<T1, T2>& p) {
    os << p.first << p.second;
    return os;
}

template <typename T>
istream& operator>>(istream& is, vector<T>& v) {
    REP(i, (int)v.size())
    is >> v[i];
    return is;
}

template <typename T>
T clamp(T& n, T a, T b) {
    if (n < a) n = a;
    if (n > b) n = b;
    return n;
}

template <typename T>
static T GCD(T u, T v) {
    T r;
    while (v != 0) {
        r = u % v;
        u = v;
        v = r;
    }
    return u;
}

template <typename T>
static T LCM(T u, T v) {
    return u / GCD(u, v) * v;
}

std::vector<int> enum_div(int n) {
    std::vector<int> ret;
    for (int i = 1; i * i <= n; ++i) {
        if (n % i == 0) {
            ret.push_back(i);
            if (i != 1 && i * i != n) { ret.push_back(n / i); }
        }
    }
    return ret;
}

template <typename T>
bool chmin(T& a, const T& b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}

template <typename T>
bool chmax(T& a, const T& b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

struct ToUpper {
    char operator()(char c) {
        return toupper(c);
    }
};

struct ToLower {
    char operator()(char c) {
        return tolower(c);
    }
};

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(20);

    string S;
    int w;
    cin >> S >> w;

    string ans = "";
    for (int i = 0; i * w < S.length(); i++) { ans.push_back(S[i * w]); }

    cout << ans << endl;
    return 0;
}
#include <bits/stdc++.h>
#define FAST ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
typedef long long ll;
typedef long double ld;
#define pb push_back
#define mp make_pair
#define ff first
#define ss second
#define mod 1000000007
#define pii pair<ll,ll>
#define inf 1000000000000000000
#define bpc(x) __builtin_popcountll(x)
#define autoit(x,it) for(auto it = x.begin(); it != x.end(); it++)
#define rep(n) for(ll i = 0; i < n; i++)
#define repi(i,n) for(ll i = 0; i < n; i++)

#include <ext/pb_ds/assoc_container.hpp> 
#include <ext/pb_ds/tree_policy.hpp> 
using namespace __gnu_pbds; 

#define ordered_set tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update> 

using namespace std;
mt19937_64 mt(chrono::steady_clock::now().time_since_epoch().count());

ll powa(ll a, ll b, ll c)
{
    a%=c;
    if(a<0)
	a+=c;
    ll res = 1;
    while(b>0)
    {
        if(b&1)
            res*=a, res%=c;
        a*=a, a%=c;
        b>>=1;
    }
    return res;
}
int main()
{
  FAST/**/
   
   ll n;
   cin>>n;
   
   ll arr[n];
   ll sum = 0;
   rep(n)
        cin>>arr[i], sum+=arr[i], sum%=mod;
   
   sum = (sum*sum)%mod;
   
   rep(n)
       sum = (sum-((arr[i]*arr[i])%mod)+mod)%mod;
   sum*=powa(2,mod-2,mod);
   sum%=mod;
   cout<<sum;
   
   return 0;        
}  

  
          
   