#line 2 "src/cp-template.hpp"
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using uint = unsigned int;
using ull  = unsigned long long;
using i128 = __int128_t;
template < class T > bool chmin(T& a, T b) { if(a > b) { a = b; return true; } return false; }
template < class T > bool chmax(T& a, T b) { if(a < b) { a = b; return true; } return false; }

#line 2 "src/utility/rep_itr.hpp"
template < class T > struct itr {
    T i, d;
    constexpr itr(const T i) noexcept : i(i), d(1) {}
    constexpr itr(const T i, const T d) noexcept : i(i), d(d) {}
    void operator++() noexcept { i += d; }
    constexpr int operator*() const noexcept { return i; }
    constexpr bool operator!=(const itr x) const noexcept {
        return d > 0 ? i < x.i : i > x.i;
    }
};

template < class T > struct rep {
    const itr< T > s, t;
    constexpr rep(const T t) noexcept : s(0), t(t) {}
    constexpr rep(const T s, const T t) noexcept : s(s), t(t) {}
    constexpr rep(const T s, const T t, const T d) noexcept : s(s, d), t(t, d) {}
    constexpr auto begin() const noexcept { return s; }
    constexpr auto end() const noexcept { return t; }
};

template < class T > struct revrep {
    const itr < T > s, t;
    constexpr revrep(const T t) noexcept : s(t - 1, -1), t(-1, -1) {}
    constexpr revrep(const T s, const T t) noexcept : s(t - 1, -1), t(s - 1, -1) {}
    constexpr revrep(const T s, const T t, const T d) noexcept : s(t - 1, -d), t(s - 1, -d) {}
    constexpr auto begin() const noexcept { return s; }
    constexpr auto end() const noexcept { return t; }
};
#line 2 "src/utility/io.hpp"
namespace scanner {
    struct sca {
        template < class T > operator T() {
            T s; cin >> s; return s;
        }
    };
    struct vec {
        int n;
        vec(int n) : n(n) {}
        template < class T > operator vector< T >() {
            vector< T > v(n);
            for(T& x : v) cin >> x;
            return v;
        }
    };
    struct mat {
        int h,w;
        mat(int h, int w) : h(h), w(w) {}
        template < class T > operator vector< vector< T > >() {
            vector m(h, vector< T >(w));
            for(vector< T >& v : m) for(T& x : v) cin >> x;
            return m;
        }
    };
    struct speedup {
        speedup() {
            cin.tie(0);
            ios::sync_with_stdio(0);
        }
    } su;
}
scanner::sca in() { return scanner::sca(); }
scanner::vec in(int n) { return scanner::vec(n); }
scanner::mat in(int h, int w) { return scanner::mat(h, w); }

namespace printer {
    void precision(int d) {
        cout << fixed << setprecision(d);
    }
    void flush() {
        cout.flush();
    }
}
int print() { cout << '\n'; return 0; }
template < class head, class... tail > int print(head&& h, tail&&... t) {
    cout << h; if(sizeof...(tail)) cout << ' ';
    return print(forward<tail>(t)...);
}
template < class T > int print(vector< T > a, char sep = ' ') {
    int n = a.size();
    for(int i : rep(n)) cout << a[i] << (i != n - 1 ? sep : '\n');
    return 0;
}
template < class T > int print(vector< vector< T > > a) {
    if(a.empty()) return 0;
    int h = a.size(), w = a[0].size();
    for(int i : rep(h)) for(int j : rep(w)) cout << a[i][j] << (j != w - 1 ? ' ' : '\n');
    return 0;
}
#line 2 "src/utility/key_val.hpp"
template < class K, class V >
struct key_val {
    K key; V val;
    key_val() {}
    key_val(K key, V val) : key(key), val(val) {}
};
#line 2 "src/utility/vec_op.hpp"
template < class T >
key_val< int, T > max_of(const vector< T >& a) {
    int i = max_element(a.begin(), a.end()) - a.begin();
    return {i, a[i]};
}

template < class T >
key_val< int, T > min_of(const vector< T >& a) {
    int i = min_element(a.begin(), a.end()) - a.begin();
    return {i, a[i]};
}

template < class T >
T sum_of(const vector< T >& a) {
    T sum = 0;
    for(const T x : a) sum += x;
    return sum;
}

template < class T >
vector<int> freq_of(const vector< T >& a, T L, T R) {
    vector<int> res(R - L);
    for(const T x : a) res[x - L]++;
    return res;
}

template < class T >
vector<int> freq_of(const vector< T >& a, T R) {
    return freq_of(a, T(0), R);
}

template < class T >
struct prefix_sum {
    vector< T > s;
    prefix_sum(const vector< T >& a) : s(a) {
        s.insert(s.begin(), T(0));
        for(int i : rep(a.size())) s[i + 1] += s[i];
    }
    // [L, R)
    T sum(int L, int R) {
        return s[R] - s[L];
    }
};
#line 1 "src/graph/shortest_path.hpp"
// g <- pair < v , cost > 
template < class T >
vector< T > dijkstra(vector<vector<pair<int, T>>> &graph, int s) {
    T INF = numeric_limits< T >::max();
    vector<T> dist(graph.size(), INF);
    priority_queue<pair<T,int>, vector<pair<T,int>>, greater<pair<T,int>>> q;
    q.push({dist[s] = T(0), s});
    while(!q.empty()){
        auto [uc, ui] = q.top(); q.pop();
        if(uc != dist[ui]) continue;
        for(auto [vi, vc] : graph[ui]) if(dist[vi] > uc + vc) 
            q.push({dist[vi] = uc + vc, vi});
    }
    return dist;
}

// g <- pair < v , cost > 
template < class T >
vector< T > dijkstra(vector<vector<pair<int, T>>> &graph, vector<int> &starts) {
    T INF = numeric_limits< T >::max();
    vector<T> dist(graph.size(), INF);
    priority_queue<pair<T,int>, vector<pair<T,int>>, greater<pair<T,int>>> q;
    for(int s : starts) q.push({dist[s] = T(0), s});
    while(!q.empty()){
        auto [uc, ui] = q.top(); q.pop();
        if(uc != dist[ui]) continue;
        for(auto [vi, vc] : graph[ui]) if(dist[vi] > uc + vc) 
            q.push({dist[vi] = uc + vc, vi});
    }
    return dist;
}

// g <- pair < v , cost > 
template < class T >
pair< T, vector<int> > shortest_path(vector<vector<pair<int, T>>> &graph, int s, int t) {
    T INF = numeric_limits< T >::max();
    vector<T> dist(graph.size(), INF);
    vector<int> prev(graph.size(), -1);
    priority_queue<pair<T,int>, vector<pair<T,int>>, greater<pair<T,int>>> q;
    q.push({dist[s] = T(0), s});
    while(!q.empty()){
        auto [uc, ui] = q.top(); q.pop();
        if(uc != dist[ui]) continue;
        for(auto [vi, vc] : graph[ui]) if(dist[vi] > uc + vc) 
            q.push({dist[vi] = uc + vc, vi}), prev[vi] = ui;
    }

    vector<int> path;
    if(dist[t] != INF) {
        for(int v = t; v != -1; v = prev[v]) path.push_back(v);
        reverse(path.begin(), path.end());
    }
    return {dist[t], path};
}
#line 3 "A.cpp"

int main() {
    ll N = in(), M = in(), C = in();
    vector<ll> A = in(N), L(M), R(M);
    for(int i : rep(M)) {
        L[i] = in(); L[i]--;
        R[i] = in();
    }
    vector<vector<pair<int,ll>>> G(N + 1);
    for(int i : rep(N)) {
        G[i + 1].push_back({i, A[i]});
        G[i].push_back({i + 1, A[i]});
    }
    for(int i : rep(M)) {
        G[L[i]].push_back({R[i], C});
        G[R[i]].push_back({L[i], C});
    }
    print(sum_of(A) - dijkstra(G, 0)[N]);
}