#include <bits/stdc++.h>
#define int long long
#pragma GCC optimize(2)
using namespace std;
const int INF = 1000000000000000000;
int n, m, k, f[100005], g[100005], a[100005], sum[100005],  b[100005], l, r, x[100005], y[100005];
inline long double slope(int q, int p) {
	return (1.0 * (y[p] - y[q])) / (x[p] - x[q]);
}
signed main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin >> n >> m >> k;
	for (int i = 2; i <= n; i++) {
		cin >> sum[i];
		sum[i] += sum[i - 1];
	}
	int p, q;
	for (int i = 1; i <= m; i++) {
		cin >> p >> q;
		a[i] = q - sum[p];
	}
	sort(a + 1, a + m + 1);
	memset(sum, 0, sizeof(sum));
	for (int i = 1; i <= m; i++) {
		sum[i] = sum[i - 1] + a[i];
	}
	k = min(k, m);
	for (int i = 1; i <= m; i++) g[i] = INF;
	g[0] = 0;
	while (k--) {
		l = r = 1;
		b[1] = 0;
		y[0] = x[0] = 0;
		for (int i = 1; i <= m; i++) {
			while (l < r && slope(b[l], b[l + 1]) <= a[i]) {
				l++;
			}
			f[i] = g[b[l]] + sum[b[l]] - sum[i] + i * a[i] - b[l] * a[i];
			y[i] = g[i] + sum[i];
			x[i] = i;
			while (l < r && slope(b[r - 1], b[r]) >= slope(b[r - 1], i)) {
				r--;
			}
			b[++r] = i;
		}
		for (int i = 1; i <= m; i++) {
			g[i] = f[i];
		}
	}
	cout << f[m];
}