//Pantyhose(black) + glasses = infinity
#include <bits/stdc++.h>
using namespace std;
#define debug(x) cerr << #x << " = " << x << '\n';
#define BP() cerr << "OK!\n";
#define PR(A, n) {cerr << #A << " = "; for (int64_t _=1; _<=n; ++_) cerr << A[_] << ' '; cerr << '\n';}
#define PR0(A, n) {cerr << #A << " = "; for (int64_t _=0; _<n; ++_) cerr << A[_] << ' '; cerr << '\n';}
#define FILE_NAME "merchant"
const int64_t MAX_N = 102;
const int64_t MAX_K = 1002;
const int64_t INF = 1e9+1e8;
struct edge {
int64_t u, v;
double w;
edge() {}
edge(int64_t u, int64_t v, double w): u(u), v(v), w(w) {}
};
int64_t n, m, k, b[MAX_N][MAX_K], s[MAX_N][MAX_K], c[MAX_N][MAX_N], mx[MAX_N][MAX_N];
vector<edge> g[MAX_N];
double d[MAX_N];
void read_input() {
cin >> n >> m >> k;
for (int64_t i=1; i<=n; ++i) {
for (int64_t j=1; j<=k; ++j)
cin >> b[i][j] >> s[i][j];
}
}
void floyd() {
for (int64_t i=1; i<=n; ++i) {
for (int64_t j=1; j<=n; ++j)
c[i][j] = INF;
}
for (int64_t i=1; i<=n; ++i)
c[i][i] = 0;
for (int64_t i=1; i<=m; ++i) {
int64_t u, v;
cin >> u >> v;
cin >> c[u][v];
}
for (int64_t k=1; k<=n; ++k) {
for (int64_t i=1; i<=n; ++i) {
for (int64_t j=1; j<=n; ++j) {
c[i][j] = min(c[i][j], c[i][k] + c[k][j]);
assert(c[i][j]>=0);
}
}
}
// debug(c[4][1]);
}
void init() {
for (int64_t i=1; i<=n; ++i) {
for (int64_t j=1; j<=n; ++j) {
mx[i][j] = -INF;
for (int64_t t=1; t<=k; ++t) {
if (b[i][t]!=-1 && s[j][t]!=-1)
mx[i][j] = max(mx[i][j], -b[i][t] + s[j][t]);
}
}
}
// debug(mx[1][4]);
}
bool relax(edge e) {
if (d[e.v]>d[e.u] + e.w) {
d[e.v] = d[e.u] + e.w;
return true;
}
return false;
}
bool check_negative_cycle(double x) {
vector<edge> E;
for (int64_t i=1; i<=n; ++i) {
for (int64_t j=1; j<=n; ++j)
E.push_back(edge(i, j, x*c[i][j] - max((int64_t)0, mx[i][j])));
}
memset(d, 0, sizeof(d));
for (int64_t i=0; i<=n; ++i) {
if (i==n)
return true;
bool stop = true;
for (auto e : E) {
if (relax(e))
stop = false;
}
if (stop)
break;
}
return false;
}
double bisect() {
double l = 0, r = INF;
while (abs(l-r)>1e-2) {
double mid = (l + r) / 2;
if (check_negative_cycle(mid))
l = mid;
else
r = mid;
}
return r;
}
int main() {
//freopen(FILE_NAME".inp", "r", stdin);
//freopen(FILE_NAME".out", "w", stdout);
ios::sync_with_stdio(0); cin.tie(0);
read_input();
floyd();
init();
// debug(check_negative_cycle(1.9));
cout << int64_t(bisect());
// for (int64_t i=1; i<=n; ++i) {
// for (int64_t j=1; j<=n; ++j) {
// if (mx[i][j]==-INF)
// cout << -1 << " \n"[j==n];
// else
// cout << mx[i][j] << " \n"[j==n];
// }
// }
}
