#include<bits/stdc++.h>
#define ll long long
#define el '\n'
#define all(a) a.begin(),a.end()

#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;
template<typename T>

using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
const ll N=1e5+5,mod=1e9+7;


void solve(ll t) {
    ll n , l;
    cin >> n >> l;

    ll sum = 0;
    while(n--)
    {
        string str;
        cin >> str;

        if (str.size() == 1)
        {
            sum += str[0]  - '0';
        }
        else
        {
            sum += (str[0]-'0')  + 1;
        }
    }


    ll ans = sum/l;
    ans--;

    if (sum % l != 0) { ans++; }

    cout << ans;

}
int main() {
    ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    ll t;
    //cin >> t;
    t = 1;
    for (ll i = 0 ; i < t ; i ++)
    {
        solve(t);
    }
}