#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 50;
int n, m, q, a[N], b[N];
long long laz[N * 4], mn[N * 4], s[N];
vector<pair<int, int> > v[N];
void build(int x, int l, int r, int op) {
  laz[x] = 0;
  if (l == r) {
    mn[x] = op ? s[l] : b[l];
    return;
  }
  int mid = (l + r) >> 1;
  build(x << 1, l, mid, op);
  build(x << 1 | 1, mid + 1, r, op);
  mn[x] = min(mn[x << 1], mn[x << 1 | 1]);
}
void push(int x, long long d) {
  mn[x] += d;
  laz[x] += d;
}
void down(int x) {
  if (laz[x]) push(x << 1, laz[x]), push(x << 1 | 1, laz[x]), laz[x] = 0;
}
void change(int x, int l, int r, int ql, int qr, int d) {
  if (l > qr || r < ql) return;
  if (l >= ql && r <= qr) {
    push(x, d);
    return;
  }
  int mid = (l + r) >> 1;
  down(x);
  change(x << 1, l, mid, ql, qr, d);
  change(x << 1 | 1, mid + 1, r, ql, qr, d);
  mn[x] = min(mn[x << 1], mn[x << 1 | 1]);
}
void change(int x, int l, int r, int p, long long d) {
  if (l == r) {
    mn[x] = d;
    return;
  }
  int mid = (l + r) >> 1;
  p <= mid ? change(x << 1, l, mid, p, d)
           : change(x << 1 | 1, mid + 1, r, p, d);
  mn[x] = min(mn[x << 1], mn[x << 1 | 1]);
}
int main() {
  scanf("%d%d%d", &n, &m, &q);
  for (int i = 1; i < n; i++) scanf("%d%d", &a[i], &b[i]);
  for (int i = 1, x, y, z; i <= m; i++) {
    scanf("%d%d%d", &x, &y, &z);
    v[x].push_back(make_pair(y, z));
  }
  build(1, 0, n - 1, 0);
  for (int i = 1; i <= n; i++) {
    for (int j = 0; j < v[i].size(); j++)
      change(1, 0, n - 1, 0, v[i][j].first - 1, v[i][j].second);
    s[i] = mn[1] + a[i];
  }
  build(1, 1, n, 1);
  printf("%lld\n", mn[1]);
  for (int i = 1, x, y; i <= q; i++) {
    scanf("%d%d", &x, &y);
    s[x] += y - a[x];
    a[x] = y;
    change(1, 1, n, x, s[x]);
    printf("%lld\n", mn[1]);
  }
}
