#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define chmin(x,y) x = min((x),(y));
#define chmax(x,y) x = max((x),(y));
using namespace std;
using ll = long long ;
using P = pair<int,int> ;
using pll = pair<long long,long long>;
const int INF = 1e9;
const long long LINF = 1e17;
const int MOD = 1000000007;
//const int MOD = 998244353;
const double PI = 3.14159265358979323846;

int main(){
    int n;
    ll x;
    cin >> n >> x;
    vector<ll> s(n);
    rep(i,n) cin >> s[i];
    rep(i,n) s[i] = x - s[i];
    ll sum = accumulate(s.begin(),s.end(),0LL);
    cout << x-sum << endl;
    return 0;
}