#include <bits/stdc++.h>
using namespace std;
const long long N = 1e6 + 5;
long long sum[N << 2], lazy[N << 2];
long long n, m, q, num, head[N], a[N], b[N];
struct node {
  long long to, nex, v;
} e[N << 1];
long long read() {
  long long x = 0, w = 1;
  char ch = getchar();
  while (ch > '9' || ch < '0') {
    if (ch == '-') w = -1;
    ch = getchar();
  }
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  return x * w;
}
void add(long long from, long long to, long long v) {
  e[++num].to = to;
  e[num].v = v;
  e[num].nex = head[from];
  head[from] = num;
}
void build(long long root, long long l, long long r) {
  long long mid = (l + r) >> 1;
  lazy[root] = 0;
  if (l == r) {
    sum[root] = b[l];
    return;
  }
  build(root << 1, l, mid);
  build(root << 1 | 1, mid + 1, r);
  sum[root] = min(sum[root << 1], sum[root << 1 | 1]);
}
void push(long long root, long long l, long long r) {
  lazy[root << 1] += lazy[root];
  lazy[root << 1 | 1] += lazy[root];
  sum[root << 1] += lazy[root];
  sum[root << 1 | 1] += lazy[root];
  lazy[root] = 0;
}
void update(long long root, long long left, long long right, long long l,
            long long r, long long v) {
  long long mid = (left + right) >> 1;
  if (left >= l && right <= r) {
    sum[root] += v;
    lazy[root] += v;
    return;
  }
  if (lazy[root]) push(root, left, right);
  if (mid >= l) update(root << 1, left, mid, l, r, v);
  if (mid < r) update(root << 1 | 1, mid + 1, right, l, r, v);
  sum[root] = min(sum[root << 1], sum[root << 1 | 1]);
}
int main() {
  n = read();
  m = read();
  q = read();
  for (long long i = 1; i < n; i++) a[i] = read(), b[i] = read();
  for (long long i = 1; i <= m; i++) {
    long long x = read(), y = read() + n, z = read();
    add(x, y, z);
  }
  build(1, 0, n - 1);
  for (long long i = 1; i <= n; i++) {
    for (long long j = head[i]; j; j = e[j].nex)
      update(1, 0, n - 1, 0, e[j].to - n - 1, e[j].v);
    b[i] = sum[1] + a[i];
  }
  build(1, 1, n);
  printf("%I64d\n", sum[1]);
  while (q--) {
    long long x = read(), y = read();
    update(1, 1, n, x, x, y - a[x]);
    a[x] = y;
    printf("%I64d\n", sum[1]);
  }
  return 0;
}
