#include <iostream>
#include <numeric>
#include <queue>
#include <vector>

template <typename T>
using min_priority_queue = std::priority_queue<T, std::vector<T>, std::greater<T>>;

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);

    int n, m;
    long long c;
    std::cin >> n >> m >> c;

    std::vector<long long> a(n);
    for (auto& e : a) {
        std::cin >> e;
    }

    std::vector<std::vector<int>> ls(n + 1), rs(n + 1);
    for (int i = 0; i < m; ++i) {
        int l, r;
        std::cin >> l >> r;
        --l;
        ls[r].push_back(l);
        rs[l].push_back(r);
    }

    long long s = std::accumulate(a.begin(), a.end(), 0LL);

    min_priority_queue<std::pair<long long, int>> pq;
    std::vector<long long> d(n + 1, 1LL << 60);
    pq.emplace(d[0] = 0, 0);
    while (pq.size()) {
        auto [du, u] = pq.top();
        pq.pop();
        if (du != d[u]) continue;

        auto update = [&](int v, long long cost) {
            if (d[v] > du + cost) pq.emplace(d[v] = du + cost, v);
        };

        if (u != 0) update(u - 1, a[u - 1]);
        if (u != n) update(u + 1, a[u]);
        for (int r : rs[u]) update(r, c);
        for (int l : ls[u]) update(l, c);
    }

    std::cout << s - d[n] << std::endl;
}