#include <bits/stdc++.h>
using namespace std;
typedef pair<int, int> PII;
const int N = 1005, INF = 0x3f3f3f3f;
vector<PII> G[N];
using namespace std;  
struct node{int col, c, id;} a[12];  
bool cmp(const node n1, const node n2) {return n1.col < n2.col;}
int n, m, dp[N][1 << 10], g[1 << 10]; bool vis[N];  
void dijkstra(int s)
{
    memset(vis, 0, sizeof(vis));
    priority_queue<PII, vector<PII>, greater<PII>> q;
    for(int i = 1; i <= n; i++) if(dp[i][s] != INF) q.push({dp[i][s], i});
    while(!q.empty())
    {
        int x = q.top().second; q.pop();
        if(vis[x]) continue;
        vis[x] = 1;
        for(auto i : G[x])
        {
            int y = i.first, w = i.second;
            if(dp[y][s] > dp[x][s] + w)
            {
                dp[y][s] = dp[x][s] + w;
                q.push({dp[y][s], y});
            }
        }
    }
}  
int solve(int cnt)  
{  
    for(int S = 1; S < (1 << cnt); S++)  
    {  
        for(int i = 1; i <= n; i++)  
        {  
            for(int s = S - 1; s; s = S & (s - 1))  
                dp[i][S] = min(dp[i][S], dp[i][s] + dp[i][S ^ s]);  
        }  
        dijkstra(S);  
    }  
    int res = INF;  
    for(int i = 1; i <= n; i++) res = min(res, dp[i][(1 << cnt) - 1]);  
    return res;  
}  

int main()  
{   
    int m, k; scanf("%d%d%d", &n, &m, &k);
    for(int i = 1, x, y, w; i <= m; i++)
    {
        scanf("%d%d%d", &x, &y, &w);
        G[x].push_back({y, w});
        G[y].push_back({x, w});
    }
    for(int i = 1; i <= k; i++) scanf("%d%d", &a[i].col, &a[i].id);  
    sort(a + 1, a + k + 1, cmp); 
    int Cn = 0;
    for(int i = 1; i <= k; i++)  // 离散化 
    {  
        if(a[i].col != a[i - 1].col) a[i].c = ++Cn;
        else a[i].c = Cn; 
    }
    memset(g, 0x3f, sizeof(g));  
    for(int S = 1; S < (1 << Cn); S++)  
    {  
        memset(dp, 0x3f, sizeof(dp));  
        int cnt = 0;   
        for(int j = 1; j <= k; j++)
            if((1 << (a[j].c - 1)) & S)
                dp[a[j].id][1 << cnt++] = 0;  
        g[S] = solve(cnt);  
    }   
    for(int S = 1; S < (1 << Cn); S++)  
        for(int s = S - 1; s; s = S & (s - 1))  
            g[S] = min(g[S], g[s] + g[S ^ s]);

    printf("%d\n", g[(1 << Cn) - 1]);
    return 0;  
}

#include <bits/stdc++.h>
using namespace std;
typedef pair<int,int> PII;
const int N=1005, INF=0x3f3f3f3f;
vector<PII>G[N];
using namespace std;  
struct node{int col,c,id;}a[12];  
bool cmp(const node n1, const node n2) {return n1.col < n2.col;}
int n,dp[N][1<<10],g[1<<10];bool vis[N];  
void dijkstra(int s)
{
	memset(vis, 0, sizeof(vis));
    priority_queue<PII,vector<PII>,greater<PII>> q;
	for(int i=1;i<=n;i++)if(dp[i][ s ]!=INF)q.push({dp[i][ s ],i});
	while(!q.empty())
	{
		int x=q.top().second;q.pop();
		if(vis[x])continue;
		vis[x]=1;
		for(auto i:G[x])
		{
			int y=i.first,w=i.second;
			if(dp[y][ s ]>dp[x][ s ]+w)
			{
				dp[y][ s ]=dp[x][ s ]+w;
				q.push({dp[y][ s ],y});
			}
		}
	}
}
int solve(int cnt)  
{  
    for(int S=1;S<(1<<cnt);S++)  
    {  
        for(int i=1;i<=n;i++)  
        {  
            for(int s=S-1;s;s=S&(s-1))  
                dp[i][S]=min(dp[i][S],dp[i][s]+dp[i][S^s]);  
        }  
        dijkstra(S);  
    }  
    int res=INF;  
    for(int i=1;i<=n;i++) res=min(res,dp[i][(1<<cnt)-1]);  
    return res;  
}  
  
int main()  
{   
    int m,k;scanf("%d%d%d",&n,&m,&k);
	for(int i=1,x,y,w;i<=m;i++)
	{
		scanf("%d%d%d",&x,&y,&w);
		G[x].push_back({y,w});
		G[y].push_back({x,w});
	}
    for(int i=1;i<=k;i++) scanf("%d%d",&a[i].col,&a[i].id);  
    sort(a+1,a+k+1,cmp); 
    int Cn=0;
    for(int i=1;i<=k;i++)  //离散化 
    {  
        if(a[i].col != a[i-1].col )a[i].c=++Cn;
        else a[i].c=Cn; 
    }
    memset(g,0x3f,sizeof(g));  
    for (int S=1;S<(1<<Cn);S++)  
    {  
        memset(dp,0x3f,sizeof(dp));  
        int cnt=0;   
        for(int j=1;j<=k;j++)
            if( (1<<a[j].c - 1) & S )
                dp[a[j].id][1<<cnt++] = 0;  
        g[S]=solve(cnt);  
     }   
    for(int S=1;S<(1<<Cn);S++)  
        for(int s=S-1;s;s=S&(s-1))  
            g[S]=min(g[S],g[s]+g[S^s]);

    printf("%d\n",g[(1<<Cn)-1]);
    return  0;  
}