#include <bits/stdc++.h>
using namespace std;
#define boost ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0)
typedef vector<int>vi;
#define pb push_back
#define all(x) begin(x), end(x)
#define sz(x) (int)x.size()
typedef pair<int,int>pi;
typedef vector<pi>vpi;
#define fi first
#define se second
#define FOR(i,a,b) for(int i=a; i<b; i++)
#define ROF(i,a,b) for(int i=b-1; i>=a; i--)
template<class T> bool ckmin(T& a, const T& b) { return a > b ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }
const int INF=2e9;
void IO() {
#ifdef LOCAL
freopen("input.txt", "r", stdin);
freopen("output.txt", "w", stdout);
#endif
}
/////////////////////////ONLY CLEAN CODES ALLOWED/////////////////////////
const int MX=1e5+10;
vi mp(MX*3,-1);
int main(){
IO(); boost;
int M;
long long L;
cin>>M>>L;
if(!(L+MX>=0 && L+MX<sz(mp))) { cout << "impossible" << endl; return 0; }
FOR(i,-M,M+1){
int n; cin>>n;
while(n--){
vpi vec;
FOR(x,0,MX*2) if(mp[x]!=-1){
vec.pb({x+i, mp[x]+1});
}
for(auto it: vec){
int k=it.fi, x=it.se;
ckmax(mp[k],x);
}
ckmax(mp[i+MX],1);
}
}
if(mp[L+MX]==-1) cout << "impossible" << endl;
else cout << mp[L+MX] << endl;
}
