#include <bits/stdc++.h>

#define int long long
#define ll long long
#define ld long double
#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
using namespace std;
int inf=2000000007;
int mod=1000000007;
int mod1=998244353;

const int N=200007;

int a[N];

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n,m,k;
    cin>>n>>m>>k;
    bool is=0;
    int ans=0,mx=0,res=0;
    for(int i=1;i<=n;i++)
    {
        cin>>a[i];
        if(i>1) ans+=min(a[i],a[i-1]);
        if(i>1) res+=abs(a[i]-a[i-1]);
        mx=max(mx,a[i]);
    }
    res+=abs(mx-a[n]);
    ans+=res/2;
    cout<<ans;

    return 0;
}