#include <bits/stdc++.h>
#define int long long
using namespace std;
const int nmax = 100;
const int kmax = 1000;
const int oo = INT_MAX;
int n,m,k;
int b[nmax + 5][kmax + 5], s[nmax + 5][kmax + 5];
int d[nmax + 5][nmax + 5], tr[nmax + 5][nmax + 5];
int rez[nmax + 5][nmax + 5];
bool ok(int cost)
{
for(int i=1; i<=n; i++)
{
for(int j=1; j<=n; j++)
{
if(tr[i][j] != -oo)
{
rez[i][j] = tr[i][j] - d[i][j] * cost;
}
else
{
rez[i][j] = -oo;
}
}
}
for(int c=1; c<=n; c++)
{
for(int i=1; i<=n; i++)
{
for(int j=1; j<=n; j++)
{
if(rez[i][c] != -oo && rez[c][j] != -oo)
{
rez[i][j] = max(rez[i][j], rez[i][c] + rez[c][j]);
}
}
}
}
for(int i=1; i<=n; i++)
{
if(rez[i][i] >= 0)
{
return true;
}
}
return false;
}
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cin>>n>>m>>k;
for(int i=1; i<=n; i++)
{
for(int j=1; j<=k; j++)
{
cin>>b[i][j]>>s[i][j];
}
}
for(int i=1; i<=n; i++)
{
for(int j=1; j<=n; j++)
{
d[i][j] = oo;
}
}
for(int i=1; i<=m; i++)
{
int x,y,c;
cin>>x>>y>>c;
d[x][y] = min(d[x][y], c);
}
for(int c=1; c<=n; c++)
{
for(int i=1; i<=n; i++)
{
for(int j=1; j<=n; j++)
{
if(d[i][c] != oo && d[c][j] != oo)
{
d[i][j] = min(d[i][j], d[i][c] + d[c][j]);
}
}
}
}
for(int i=1; i<=n; i++)
{
for(int j=1; j<=n; j++)
{
tr[i][j] = 0;
for(int it=1; it<=k; it++)
{
if(b[i][it] == -1 || s[j][it] == -1 || d[i][j] == oo)
{
continue;
}
tr[i][j] = max(tr[i][j], s[j][it] - b[i][it]);
}
}
}
int st = 0;
int dr = 1e9;
int rez = 0;
while(st<=dr)
{
int mij = (st + dr) >> 1;
if(ok(mij))
{
rez = mij;
st = mij + 1;
}
else
{
dr = mij - 1;
}
}
cout<<rez<<'\n';
return 0;
}
