#include <bits/stdc++.h>
#define FOR(i,j,k) for(int i=j; i<=k; ++i)
#define ROF(i,j,k) for(int i=j; i>=k; --i)
inline int read (void) {
int x = 0, f = 1, ch = getchar();
while(!isdigit(ch)) { if(ch == '-') f = -f; ch = getchar(); }
while(isdigit(ch)) { x = x * 10 + ch - '0'; ch = getchar(); }
return x * f;
}
using ll = long long;
const int maxn = 105;
const int maxk = 1005;
int b[maxn][maxk], s[maxn][maxk], e[maxn][maxn];
ll d[maxn][maxn], f[maxn][maxn];
int main (void) {
int n = read(), m = read(), k = read();
FOR(i,1,n) FOR(j,1,k) {
b[i][j] = read(), s[i][j] = read();
if(b[i][j] == -1) b[i][j] = 1 << 30;
if(s[i][j] == -1) s[i][j] = 0;
}
FOR(i,1,n) FOR(j,1,n) FOR(t,1,k)
e[i][j] = std::max(e[i][j], s[j][t] - b[i][t]);
FOR(i,1,n) FOR(j,1,n) d[i][j] = 1 << 30;
FOR(i,1,m) {
int x = read(), y = read(), c = read();
d[x][y] = c;
}
FOR(i,1,n) d[i][i] = 0;
FOR(t,1,n) FOR(i,1,n) FOR(j,1,n) d[i][j] = std::min(d[i][j], d[i][t] + d[t][j]);
int left = 1, right = 1e9, mid, ans = 0;
while(left <= right) {
mid = (left + right >> 1);
FOR(i,1,n) FOR(j,1,n) f[i][j] = i == j ? -1ll << 60 : e[i][j] - 1ll * mid * d[i][j];
FOR(t,1,n) FOR(i,1,n) FOR(j,1,n) f[i][j] = std::max(f[i][j], f[i][t] + f[t][j]);
bool flag = 0; FOR(i,1,n) if(f[i][i] >= 0) { flag = 1; break; }
if(flag) ans = mid, left = mid + 1; else right = mid - 1;
}
printf("%d\n", ans);
return 0;
}
