#include <iostream>
#include <vector>
#include <set>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <stdio.h>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <fstream>
#include <complex>
#include <random>
#include <stack>
#include <chrono>
#include <set>
#define FOR(i,n) for(int i=0;i<n;i++)
#define FORE(i,a,b) for(int i=a;i<=b;i++)
#define ll long long int
#define vi vector<int>
#define ii pair<int,int>
#define pb push_back
#define mp make_pair
#define ff first
#define il pair<int,ll>
#define li pair<ll,int>
#define ss second
#define pll pair<ll,ll>
#define cd complex<double>
#define ld long double
#define pld pair<ld,ld>
#define plli pair<pll,ll>
#define vv vector
using namespace std;
const ld INF = 1e18;
const int MAXN = 100 + 10;
const int MAXK = 1000 + 10;
vv<ll> B[MAXN];
vv<ll> S[MAXN];
ll mat[MAXN][MAXN];
ll dist1[MAXN][MAXN];
ll profit[MAXN][MAXN];
int n,m,k;
void precomp(){
FOR(i,n)FOR(j,n)dist1[i][j] = mat[i][j];
FOR(conn,n){
FOR(i,n){
FOR(j,n){
if(dist1[i][conn] + dist1[conn][j] < dist1[i][j]){
dist1[i][j] = dist1[i][conn] + dist1[conn][j];
}
}
}
}
FOR(i,n){
FOR(j,n){
FOR(item,k){
if(B[i][item] == -1 or S[j][item] == -1)continue;
profit[i][j] = max(profit[i][j] , S[j][item] - B[i][item]);
}
}
}
}
ld route[MAXN][MAXN];
bool isPoss(ld x){
FOR(i,n){
FOR(j,n){
if(i == j) route[i][j] = -INF;
else route[i][j] = profit[i][j] - x*dist1[i][j];
}
}
FOR(conn,n){
FOR(i,n){
FOR(j,n){
if(route[i][conn] + route[conn][j] > route[i][j]){
route[i][j] = route[i][conn] + route[conn][j];
}
}
}
}
FOR(i,n)if(route[i][i] >= 0)return 1;
return 0;
}
int main(){
cin >> n >> m >> k;
FOR(i,n){
FOR(j,k){
int a,b;
cin >> a >> b;
B[i].pb(a);
S[i].pb(b);
}
}
FOR(i,n)FOR(j,n)mat[i][j] = INF;
FOR(i,m){
int a,b,c;
cin >> a >> b >> c;
a--;b--;
mat[a][b] = c;
}
precomp();
//cout << isPoss(2) << endl;
FOR(i,n){
FOR(j,n){
//cout << dist1[i][j] << " ";
}
//cout << endl;
}
ld lo = 0;
ld hi = INF;
ld eps = 0.0001;
ld best = 0;
while(hi-lo > eps){
ld mid = (hi + lo)/2;
//cout << setprecision(10) << hi << " " << mid << " " << lo << endl;
if(isPoss(mid)){
best = max(best,mid);
lo = mid;
}else{
hi = mid;
}
}
if(isPoss((ll)hi))best = max(best,(ld)((ll)hi));
cout << (ll)best << endl;
return 0;
}
