#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
ll buy[105][1005];
ll sell[105][1005];
ll dist[1005][1005];
ll graf[1005][1005];
ll prof[1005][1005];
ll tren[1005][1005];
const ll INF = 1000000000000000LL;
int n;
bool check(ll val){
for(int i=1; i<=n; i++){
for(int j=1; j<=n; j++){
tren[i][j] = - prof[i][j] + dist[i][j]*val;
// cout << i << " " << j << " " << tren[i][j] << endl;
}
}
for(int k=1; k<=n; k++){
for(int i=1; i<=n; i++){
for(int j=1; j<=n; j++){
tren[i][j] = min(tren[i][j], tren[i][k] + tren[k][j]);
}
}
}
for(int k=1; k<=n; k++){
for(int i=1; i<=n; i++){
for(int j=1; j<=n; j++){
if(tren[i][j] > tren[i][k] + tren[k][j]) return 1;
}
}
}
return 0;
}
int main(){
ios_base::sync_with_stdio(false), cin.tie(0);
cout.precision(0);
cout << fixed;
int m, K;
cin >> n >> m >> K;
for(int i=1; i<=n; i++){
for(int j=1; j<=K; j++){
cin >> buy[i][j];
cin >> sell[i][j];
//buy[i][j] *= 2;
//sell[i][j] *= 2;
}
}
for(int i=1; i<=n; i++){
for(int j=1; j<=n; j++){
dist[i][j] = graf[i][j] = INF;
}
dist[i][i] = graf[i][i] = 0;
}
for(int i=1; i<=m; i++){
ll a, b, c;
cin >> a >> b >> c;
//c *= 2;
dist[a][b] = graf[a][b] = min(graf[a][b], c);
}
for(int k=1; k<=n; k++){
for(int i=1; i<=n; i++){
for(int j=1; j<=n; j++){
dist[i][j] = min(dist[i][j], dist[i][k] + dist[k][j]);
}
}
}
for(int i=1; i<=n; i++){
for(int j=1; j<=n; j++){
if(i == j) continue;
for(int k=1; k<=K; k++){
if(buy[i][k]+1 && sell[j][k]+1) prof[i][j] = max(prof[i][j], sell[j][k]-buy[i][k]);
}
//cout << i << " " << j << " za " << prof[i][j] << endl;
}
}
ld res = 0, l = 1, r = 2000000000, tries = 100;
while(tries--){
ld mid = (l+r)/2;
if(check(mid)){
res = mid;
l = mid+0.001;
}
else r = mid-0.001;
}
cout << res << endl;
return 0;
}
