#include<bits/stdc++.h>
using namespace std;
#define int long long
#define F first
#define S second
#define pii pair<int,int>
#define mpr make_pair
typedef long long ll;
typedef long double ld;
const int maxn = 105;
const int mod = 1e9+7;
const ll inf = 1e9+10;
const int MAX_K = 1010;
int n, m, k;
ld dis[maxn][maxn], W[maxn][maxn];
ld buy[maxn][MAX_K], sell[maxn][MAX_K];
ld dp[maxn];
bool ok(ld q)
{
/// negetive cycle
fill(dp, dp+n+1, inf*inf);
dp[1] = 0;
for(int I = 1; I <= n; I++)
for(int u = 1; u <= n; u++)
for(int v = 1; v <= n; v++)
{
// if(I == 3)
// cout<< u <<" "<< v <<" "<< fixed << setprecision(40) <<" "<< (-W[u][v] + dis[u][v] * q) <<"\n";
if(dp[v] > dp[u] + (-W[u][v] + dis[u][v] * q))
{
if(I == n) return 1;
dp[v] = dp[u] + (-W[u][v] + dis[u][v] * q);
}
}
return 0;
}
signed main()
{
//ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin>> n >> m >> k;
for(int i = 1; i <= n; i++)
{
for(int j = 1; j <= n; j++) dis[i][j] = inf;
dis[i][i] = 0;
}
for(int i = 1; i <= n; i++)
for(int j = 1; j <= k; j++)
cin>> buy[i][j] >> sell[i][j];
for(int i = 1, u, v; i <= m; i++)
{
ld w; cin>> u >> v >> w;
dis[u][v] = min(dis[u][v], w);
}
/// floyd
for(int k = 1; k <= n; k++)
for(int u = 1; u <= n; u++)
for(int v = 1; v <= n; v++)
dis[u][v] = min(dis[u][v], dis[u][k] + dis[k][v]);
/// end
for(int u = 1; u <= n; u++)
{
for(int v = 1; v <= n; v++)
{
W[u][v] = 0.0;
for(int x = 1; x <= k; x++)
if(buy[u][x] != -1 && sell[v][x] != -1)
W[u][v] = max(W[u][v], -buy[u][x] + sell[v][x]);
// cout<< u <<" "<< v <<" "<< W[u][v] <<" "<< dis[u][v] <<"\n";
}
}
ld eps = 1.0/(1e18);
ll lo = 0, hi = inf;
while(hi-lo > 1)
{
ll tm = (hi + lo) >> 1;
if(ok(tm)) lo = tm;
else hi = tm;
}
ld x = hi;
if(ok(x-eps)) cout<< hi <<" ";
else cout<< lo;
}
/*
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
*/
