// i don't understand
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll INFL = 2e18;
const int MN = 105;
const int MK = 1010;
ll am[MN][MN];
ll pr[MN][MN];
ll ro[MN][MN];
ll bro[MN][MK],slo[MN][MK];
int main() {
ios::sync_with_stdio(0);cin.tie(0);
ll n,m,ks;
cin >> n >> m >> ks;
for(int i=0;i<n;i++) {
for(int j=0;j<n;j++) {
am[i][j] = INFL;
}
}
for(int i=0;i<n;i++) {
for(int j=0;j<ks;j++) {
cin >> bro[i][j] >> slo[i][j];
}
}
for(int i=0;i<m;i++) {
ll a,b,c;
cin >> a >> b >> c;
a--;b--;
am[a][b] = c;
}
for(int k=0;k<n;k++) {
for(int i=0;i<n;i++) {
for(int j=0;j<n;j++) {
am[i][j] = min(am[i][j],am[i][k]+am[k][j]);
}
}
}
memset(pr,0,sizeof(pr));
for(int i=0;i<n;i++) {
for(int j=0;j<n;j++) {
for(int k=0;k<ks;k++) {
if(slo[j][k] == -1) {continue;}
if(bro[i][k] == -1) {continue;}
pr[i][j] = max(pr[i][j],slo[j][k]-bro[i][k]);
}
}
}
ll st = 1,ed = 1e9+2;
ll ls = 0;
while(st <= ed) {
ll md = (st+ed)/2;
for(int i=0;i<n;i++) {
for(int j=0;j<n;j++) {
if(i == j) {
ro[i][j] = -1;
} else if(am[i][j] == INFL) {
ro[i][j] = -INFL;
} else {
ro[i][j] = pr[i][j]-md*am[i][j];
}
}
}
for(int k=0;k<n;k++) {
for(int i=0;i<n;i++) {
for(int j=0;j<n;j++) {
ro[i][j] = max(ro[i][j],ro[i][k]+ro[k][j]);
ro[i][j] = min(ro[i][j],INFL);
}
}
}
bool lol = false;
for(int i=0;i<n;i++) {
if(ro[i][i] >= 0) {
lol = true;break;
}
}
if(lol) {
ls = md;
st = md+1;
} else {
ed = md-1;
}
}
cout << ls << '\n';
}
