#include<bits/stdc++.h>
using namespace std;
#define ll long long
int s[101][1000];
int b[101][1000];
int d[101][101];
int w[101][101];
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; cin >> n;
int m; cin >> m;
int k; cin >> k;
for(int i = 0 ; i < n ; ++i)
for(int j = 0 ; j < k ; ++j)
cin >> b[i][j],
cin >> s[i][j];
memset(d,0x3f,sizeof d);
for(int i = 0 ; i < n ; ++i) d[i][i] = 0;
for(int i = 0 ; i < m ; ++i) {
int x; cin >> x; --x;
int y; cin >> y; --y;
int t; cin >> t;
d[x][y] = t;
d[y][x] = t;
}
for(int T = 0 ; T < n ; ++T)
for(int i = 0 ; i < n ; ++i)
for(int j = 0 ; j < n ; ++j)
d[i][j] = min(d[i][j],d[i][T] + d[T][j]);
for(int P = 0 ; P < k ; ++P)
for(int i = 0 ; i < n ; ++i)
for(int j = 0 ; j < n ; ++j) if (b[i][P] >= 0 && s[j][P] >= 0)
w[i][j] = max(w[i][j],s[j][P] - b[i][P]);
vector<vector<ll> > dd(n,vector<ll>(n));
int l = 0;
int r = 1e9 + 7;
for(; l < r ;) {
m = (l + r + 2) / 2;
for(int i = 0 ; i < n ; ++i)
for(int j = 0 ; j < n ; ++j)
dd[i][j] = 1ll * m * d[i][j] - w[i][j];
for(int T = 0 ; T < n ; ++T)
for(int i = 0 ; i < n ; ++i)
for(int j = 0 ; j < n ; ++j)
dd[i][j] = min(dd[i][j],dd[i][T] + dd[T][j]);
bool ok = 0;
for(int i = 0 ; i < n ; ++i)
if (dd[i][i] <= 0) {
ok = 1;
break;
}
if (ok) l = m;
else r = m - 1;
}
cout << l << endl;
}
/*
4 5 2
10 9 5 2
6 4 20 15
9 7 10 9
-1 -1 16 11
1 2 3
2 3 3
1 4 1
4 3 1
3 1 1
*/
