1 #include<iostream>
2 #include<cstring>
3 #include<string>
4 #include<cmath>
5 #include<cstdio>
6 #include<queue>
7 #define ll long long
8 #define INF 1e16
9 using namespace std;
10 const int N = 8e5 + 10;
11 struct edge
12 {
13 int u, to, next;
14 ll w;
15 }e[N];
16 int head[N], cnt[N];
17 ll dis[N];
18 bool vis[N];
19 int tot;
20
21 typedef pair<ll, int> pii;
22
23 void init()
24 {
25 for(int i = 0 ; i < N ; i++){
26 e[i].next = -1;
27 head[i] = -1;
28 vis[i] = false;
29 }
30 tot = 0;
31 for(int i = 0 ; i < N ; i++){
32 dis[i] = INF;
33 }
34 }
35
36 inline void add(int u, int v, ll w)
37 {
38 e[tot].u = u;
39 e[tot].to = v;
40 e[tot].w = w;
41 e[tot].next = head[u];
42 head[u] = tot++;
43 }
44
45 void JK(int now)
46 {
47 dis[now] = 0;//
48 priority_queue<pii, vector<pii>, greater<pii> >q;//
49 q.push(make_pair(dis[now], now));
50 while(!q.empty()){
51 pii tmp = q.top();
52 q.pop();
53 ll d = tmp.first;
54 int u = tmp.second;
55 if(vis[u]) continue;
56 vis[u] = true;
57 for(int i = head[u] ; ~i ; i = e[i].next){
58 int v = e[i].to;
59 if(e[i].w + d == dis[v]){
60 cnt[v]++;
61 }
62 if(e[i].w + d < dis[v]){
63 cnt[v] = 1;
64 dis[v] = e[i].w + d;
65 q.push(make_pair(dis[v], v));
66 }
67 }
68 }
69 }
70
71 int n, m, k;
72
73 int main(){
74 scanf("%d%d%d",&n,&m,&k);
75 init();
76 for(int i = 1 ; i <= m ; i++){
77 int u, v, w;
78 scanf("%d%d%lld",&u,&v,&w);
79 add(u, v, w);
80 add(v, u, w);
81 }
82 for(int i = 1 ; i <= k ; i++){
83 int v, w;
84 scanf("%d%lld",&v,&w);
85 add(1, v, w);
86 add(v, 1, w);
87 }
88
89 JK(1);
90 int ans = 0;
91 for(int i = (m << 1), c = 1 ; c <= k ; c++, i += 2){
92 int v = e[i].to, w = e[i].w;
93 if(dis[v] < w){
94 ans++;
95 }else if(dis[v] == w){
96 if(cnt[v] > 1){
97 ans++;
98 cnt[v]--;
99 }
100 }
101 }
102 printf("%d\n",ans);
103
104 return 0;
105 }
