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Posted 2021-02-17 violet-acmer

#include<bits/stdc++.h>
using namespace std;
//#include<ext/rope>
//using namespace __gnu_cxx
//#include<ext/pb_ds/priority_queue.hpp>
//using namespace __gnu_pbds;
#define lowbit(x) (x&-x)
#define pb(x) push_back(x)
#define all(x) (x).begin(),(x).end()
#define clr(a,b) memset(a,b,sizeof(a))
#define caze(T) for(scanf("%d",&T);T;T--)
#define inf (1<<30)
#define Endl (‘
‘)
#define fi first
#define se second
#define db double
#define ldb long double
#define ll long long
#define pll pair<ll,ll>
#define pli pair<ll,int>
#define pii pair<int,int>
#define ull unsigned long long
#define ios ios::sync_with_stdio(0),cin.tie(0),cout.tie(0)
ll dp[300030][3];    //0:unuse,1:using,2:used
ll a[300030];
int main()
{
    int n;
    ll x;
    ll ans=0;
    cin>>n>>x;
    for(int i=1;i<=n;++i)
        cin>>a[i];
    clr(dp[0],0);
    for(int i=1;i<=n;++i)
    {
        dp[i][0]=max(dp[i-1][0],0LL)+a[i];
        dp[i][1]=max(0LL,max(dp[i-1][0],dp[i-1][1]))+a[i]*x;
        dp[i][2]=max(0LL,max(dp[i-1][1],dp[i-1][2]))+a[i];
        for(int j=0;j<3;++j)
            ans=max(ans,dp[i][j]);
    }
    cout<<ans<<Endl;
}