#include <bits/stdc++.h>

#define rep(i, a, b) for(int i = (a); i <= (b); i ++)
using std::cin, std::cout, std::cerr;
using ll = long long;

void Solve() {
    int n, m; ll c; cin >> n >> m >> c;
    std::vector<std::vector<std::pair<int, ll>>> e(n + 1);
    ll sum = 0;
    rep(i, 1, n) {
        ll x; cin >> x;
        sum += x;
        e[i - 1].push_back({i, x});
        e[i].push_back({i - 1, x});
    }
    rep(i, 1, m) {
        int l, r; cin >> l >> r;
        e[l - 1].push_back({r, c});
        e[r].push_back({l - 1, c});
    }

    std::vector<ll> f(n + 1, 1e18L);
    f[0] = 0;
    std::set<std::pair<ll, int>> set;
    rep(i, 0, n) set.insert({f[i], i});
    while(!set.empty()) {
        auto [_, x] = *set.begin();
        set.erase(set.begin());

        for(auto [i, w] : e[x]) {
            if(f[x] + w < f[i]) {
                set.erase({f[i], i});
                f[i] = f[x] + w;
                set.insert({f[i], i});
            }
        }
    }
    cout << sum - f[n] << '\n';
}

int main() {
    std::ios::sync_with_stdio(false);
    int T = 1;
    while(T --) {
        Solve();
    }
}