#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N=2e5+5;
int n,m,C,a[N];
ll d[N];
bool v[N];
vector<pair<int,int>>e[N];
void Addedge(int x,int y,int w) {e[x].emplace_back(y,w),e[y].emplace_back(x,w);}
signed main()
{
	ios::sync_with_stdio(0),cin.tie(0);
	cin>>n>>m>>C;
	ll sum=0;
	for(int i=1,a;i<=n;i++) cin>>a,sum+=a,Addedge(i,i+1,a);
	for(int i=1,l,r;i<=m;i++) cin>>l>>r,Addedge(l,r+1,C);
	priority_queue<pair<ll,int>>pq;
	memset(d,0x3f,sizeof(d)),d[1]=0,pq.emplace(0,1);
	while(!pq.empty())
	{
		int x=pq.top().second; pq.pop();
		if(v[x]) continue;
		v[x]=1;
		for(auto it:e[x])
		{
			int y,w; tie(y,w)=it;
			if(!v[y]&&d[x]+w<d[y]) d[y]=d[x]+w,pq.emplace(-d[y],y);
		}
	}
	cout<<sum-d[n+1]<<"\n";
	return 0;
}