#include<bits/stdc++.h>
#define int long long
using namespace std;
signed main(){
    int N,X,sum=0;cin>>N>>X;
    vector<int>A(N);
    for(int&i:A){
        cin>>i;
        i=X-i;
        sum+=i;
    }
    cout<<(X-sum)<<endl;
}