//雪花飄飄北風嘯嘯
//天地一片蒼茫
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;
#define ll long long
#define ii pair<ll,ll>
#define iii pair<ii,ll>
#define fi first
#define se second
#define endl '\n'
#define debug(x) cout << #x << " is " << x << endl;
#define rep(x,start,end) for(auto x=(start)-((start)>(end));x!=(end)-((start)>(end));((start)<(end)?x++:x--))
#define all(x) (x).begin(),(x).end()
#define sz(x) (int)(x).size()
ll MAX(ll a){return a;}
ll MIN(ll a){return a;}
template<typename... Args>
ll MAX(ll a,Args... args){return max(a,MAX(args...));}
template<typename... Args>
ll MIN(ll a,Args... args){return min(a,MIN(args...));}
#define indexed_set tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>
mt19937 rng(chrono::system_clock::now().time_since_epoch().count());
int n,m,k;
ll buy[105][1005];
ll sell[105][1005];
ll dist[105][105];
ll val[105][105];
ll APSP[105][105];
bool can(ll i){
rep(x,0,n) rep(y,0,n){
APSP[x][y]=val[x][y]-dist[x][y]*i;
}
rep(k,0,n){
rep(i,0,n){
rep(j,0,n){
APSP[i][j]=max(APSP[i][j],APSP[i][k]+APSP[k][j]);
}
}
}
rep(x,0,n) if (APSP[x][x]>=0) return true;
return false;
}
int main(){
ios::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>n>>m>>k;
rep(x,0,n) rep(y,0,k){
cin>>buy[x][y]>>sell[x][y];
if (buy[x][y]==-1) buy[x][y]=1e18;
if (sell[x][y]==-1) sell[x][y]=-1e18;
}
rep(x,0,n) rep(y,0,n) dist[x][y]=1e9;
int a,b,c;
rep(x,0,m){
cin>>a>>b>>c;
a--,b--;
dist[a][b]=c;
}
rep(k,0,n){
rep(i,0,n){
rep(j,0,n){
dist[i][j]=min(dist[i][j],dist[i][k]+dist[k][j]);
}
}
}
rep(x,0,n) rep(y,0,n){
rep(z,0,k) val[x][y]=max(val[x][y],sell[y][z]-buy[x][z]);
}
ll lo=0,hi=1e9+100,mi;
while (hi-lo>1){
mi=hi+lo>>1;
if (can(mi)) lo=mi;
else hi=mi;
}
cout<<lo<<endl;
}
