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

int c, n, m, ecnt, s[200024], ev[800024], ex[800024];
long long dis[200024], ew[800024];
char vis[200024];

void add(int u, int v, long long w) {
    ev[++ecnt] = v, ex[ecnt] = s[u], ew[ecnt] = w, s[u] = ecnt;
    ev[++ecnt] = u, ex[ecnt] = s[v], ew[ecnt] = w, s[v] = ecnt;
}

void spfa() {
    for (int i = 1; i <= n + 1; i++) vis[i] = 0, dis[i] = 0x3f3f3f3f3f3f3f3f;
    priority_queue<pair<long long, int>, vector<pair<long long, int>>, greater<pair<long long, int>>> q;
    dis[1] = 0;
    q.push({0, 1});
    for (int i = 1; i <= n + 1; i++) {
        int u = q.top().second;
        q.pop();
        while (vis[u]) u = q.top().second, q.pop();
        vis[u] = 1;
        for (int i = s[u]; i; i = ex[i]) {
            int v = ev[i];
            if (vis[v] || dis[u] + ew[i] > dis[v]) continue;
            dis[v] = dis[u] + ew[i];
            q.push({dis[v], v});
        }
    }
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    long long ans = 0;
        cin >> n >> m >> c;
        for (int i = 1; i <= n; i++) {
            int tmp;
            cin >> tmp;
            ans += tmp;
            add(i, i + 1, tmp);
        }
        for (int i = 1; i <= m; i++) {
            int u, v;
            cin >> u >> v;
            add(u, v + 1, c);
        }
        spfa();
        ans -= dis[n + 1];
        cout << ans << '\n';
return 0;
}