代码，0分

#include<bits/stdc++.h>
using namespace std;
int a[5000006];
int ans = -1e9 , sum , num;
int main(){
    int n , m , _a;
    cin >> n >> m >> _a;
    cin >> a[1];
    for(int i = 2 ; i <= n ; i++){
        cin >> a[i];
        sum += max(a[i] , a[i - 1]);
    }
    num = sum;
    for(int i = 1 ; i <= n + 1 ; i++){
        sum -= max(a[i] , a[i - 1]);
        sum = sum + max(_a , a[i - 1]) + max(_a , a[i]);
        ans = max(ans , sum);
        sum = num;
    }
    cout << ans;
    return 0;
}