/*
Task : Travelling_Merchant
Author : Phumipat C. [MAGCARI]
Language: C++
Created : 18 May 2021 [15:03]
Algo :
Status :
*/
#include<bits/stdc++.h>
#define rep(i, a, b) for(int i = a; i <= (b); ++i)
#define repr(i, a, b) for(int i = a; i >= (b); --i)
#define all(x) begin(x),end(x)
#define allst(x,y) (x).begin()+y,(x).end()
#define rmdup(x) (x).resize(unique((x).begin(),(x).end())-(x).begin())
#define sz(x) (int)(x).size()
#define decp(x) fixed << setprecision(x)
#define MOD (LL )(1e9+7)
using namespace std;
using LL = long long;
using PII = pair<int ,int >;
using PLL = pair<long long ,long long >;
const int dir4[2][4] = {{1,-1,0,0},{0,0,1,-1}};
const int dir8[2][8] = {{-1,-1,-1,0,1,1,1,0},{-1,0,1,1,-1,0,1,-1}};
LL modN(LL a,LL b,LL c = MOD){
if(b == 0) return 1;
if(b == 1) return a%c;
LL now = modN(a,b/2,c);
if(b&1) return (((now*now)%c)*(a%c))%c;
else return (now*now)%c;
}
const int N = 110;
const int mxK = 1010;
LL prof[N][N],dis[N][N],eff[N][N],buy[N][mxK],sell[N][mxK];
int n,m,K;
bool check(LL val){
rep(i,1,n) rep(j,1,n) eff[i][j] = -1e18;
rep(i,1,n){
rep(j,1,n){
if(dis[i][j] == 1e18) continue;
eff[i][j] = max(eff[i][j],prof[i][j] - val*dis[i][j]);
}
}
rep(k,1,n){
rep(i,1,n){
rep(j,1,n){
eff[i][j] = max(eff[i][j],eff[i][k] + eff[k][j]);
}
}
}
rep(i,1,n)
if(eff[i][i]>=0)
return true;
return false;
}
void solve(){
int u,v;
LL w;
cin >> n >> m >> K;
rep(i,1,n)
rep(j,1,K)
cin >> buy[i][j] >> sell[i][j];
rep(i,1,n) rep(j,1,n) dis[i][j] = 1e18;
while(m--){
cin >> u >> v >> w;
dis[u][v] = min(dis[u][v],w);
}
rep(k,1,n){
rep(i,1,n){
rep(j,1,n){
if(dis[i][k] == 1e18 || dis[k][j] == 1e18) continue;
dis[i][j] = min(dis[i][j],dis[i][k] + dis[k][j]);
}
}
}
rep(l,1,K){
rep(i,1,n){
rep(j,1,n){
if(dis[i][j] == 1e18 || buy[i][l] == -1 || sell[j][l] == -1) continue;
prof[i][j] = max(prof[i][j],sell[j][l] - buy[i][l]);
}
}
}
LL l = 0,r = 1e9,mid;
while(l<r){
mid = (l+r+1)/2;
if(check(mid)) l = mid;
else r = mid-1;
}
cout << l << '\n';
}
int main(){
cin.tie(0)->sync_with_stdio(0);
cin.exceptions(cin.failbit);
int q = 1;
// cin >> q;
for(int Q=1;Q<=q;Q++){
// cout << "Case #" << Q << ": ";
solve();
}
return 0;
}
