#include <bits/stdc++.h>
using namespace std;
using ll = long long;

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m, c, v, u, L, R;
    ll d, w;
    cin >> n >> m >> c;
    vector<vector<pair<int, ll>>> g(n + 1);
    vector<int> a(n);
    vector<ll> as(n + 1), dist(n + 1, 1ll << 60);
    for(int i = 0; i < n; i++){
        cin >> a[i];
        as[i + 1] = as[i] + a[i];
        g[i].emplace_back(i + 1, a[i]);
        g[i + 1].emplace_back(i, a[i]);
    }
    for(int i = 0; i < m; i++){
        cin >> L >> R;
        L--;
        g[L].emplace_back(R, c);
    }
    priority_queue<pair<ll,int>, vector<pair<ll,int>>, greater<pair<ll,int>>> pq;
    dist[0] = 0;
    pq.emplace(0, 0);
    while(!pq.empty()){
        tie(d, v) = pq.top();
        pq.pop();
        if(d > dist[v]) continue;
        for(auto &&pa : g[v]){
            tie(u, w) = pa;
            if(d + w >= dist[u]) continue;
            dist[u] = d + w;
            pq.emplace(dist[u], u);
        }
    }
    cout << as[n] - dist[n] << '\n';
}