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

const int N = 2e5 + 5;
const long long INF = 1e18;
int n, m, w, vis[N]; long long dis[N];
vector<pair<int, int>> e[N];

int main() {
    ios :: sync_with_stdio(false), cin.tie(0);
    
    cin >> n >> m >> w;
    long long sumA = 0;
    for (int i = 1; i <= n; i++) {
        int a; cin >> a; sumA += a;
        e[i].emplace_back(i + 1, a);
        e[i + 1].emplace_back(i, a);
    }
    for (int i = 1; i <= m; i++) {
        int l, r; cin >> l >> r;
        e[l].emplace_back(r + 1, w);
        e[r + 1].emplace_back(l, w);
    }
    
    fill(dis + 1, dis + 2 + n, INF);
    priority_queue<pair<long long, int>> q;
    q.push({dis[1] = 0, 1});
    while (!q.empty()) {
        int x = q.top().second; q.pop();
        if (vis[x]) { continue; } vis[x] = 1;
        for (auto i : e[x]) {
            int y = i.first;
            long long v = dis[x] + i.second;
            if (v < dis[y]) { q.push({-(dis[y] = v), y}); }
        }
    }
    cout << sumA - dis[n + 1] << "\n";
    
    return 0;
}