#include <bits/stdc++.h>#define N 60#define INF 1000000000using namespace std;int n, m, nn;double ai[N], an[N], ci[2][N][N], ans;int bc[N];int ini[N], vis[N], inc[N], inl[N];int dfn;int dfs(int t){    vis[t] = dfn;    if (vis[ini[t]] == vis[t])        return ini[t];    else if (vis[ini[t]])         return 0;    else return dfs(ini[t]);} int main(){    scanf("%d", &n);    for (int i = 0; i <= n; ++ i)        for (int j = 0; j <= n; ++ j)            ci[0][i][j] = INF;    for (int i = 1; i <= n; ++ i)        scanf("%lf%d", &ai[i], &bc[i]), an[i] = ai[i], ci[0][0][i] = ai[i];    scanf("%d", &m);    for (int i = 1; i <= m; ++ i)    {        int a, b; double c;        scanf("%d%d%lf", &a, &b, &c);        if (a != b) ci[0][a][b] = min(ci[0][a][b], c);        an[b] = min(an[b], c);    }    for (int i = 1; i <= n; ++ i) ans += an[i] * (bc[i] - 1);    int tmp = 0, wh = 1; nn = n;    while (wh)    {        wh = 0;        for (int i = 1; i <= nn; ++ i)        {            double mn = INF;            for (int j = 0; j <= nn; ++ j)                if (ci[tmp][j][i] < mn)                    mn = ci[tmp][j][i], ini[i] = j;        }        for (int i = 0; i <= nn; ++ i) vis[i] = 0; vis[0] = -1;        for (int i = 1; i <= nn; ++ i)            if (!vis[i])            {                dfn ++;                int x = dfs(i);                if (x)                {                    int tot = 0;                    wh = 1;                    for (int j = 0; j <= nn; ++ j) inc[j] = 0;                    for (int j = ini[x]; j != x; j = ini[j]) inc[j] = 1; inc[x] = 1;                    for (int j = 0; j <= nn; ++ j) if (!inc[j]) inl[j] = tot ++; else ans += ci[tmp][ini[j]][j];                    for (int j = 0; j <= nn; ++ j)                        for (int k = 0; k <= nn; ++ k)                            ci[!tmp][j][k] = INF;                    for (int j = 0; j <= nn; ++ j)                        for (int k = 0; k <= nn; ++ k)                        {                            if (!inc[j])                            {                                if (!inc[k])                                    ci[!tmp][inl[j]][inl[k]] = min(ci[!tmp][inl[j]][inl[k]], ci[tmp][j][k]);                                else                                    ci[!tmp][inl[j]][tot] = min(ci[!tmp][inl[j]][tot], ci[tmp][j][k] - ci[tmp][ini[k]][k]);                            }                            else if (!inc[k])                                    ci[!tmp][tot][inl[k]] = min(ci[!tmp][tot][inl[k]], ci[tmp][j][k]);                        }                    nn = tot;                    break;                }            }        if (!wh)            for (int i = 1; i <= nn; ++ i) ans += ci[tmp][ini[i]][i];        else tmp ^= 1;    }    printf("%.2lf", ans);}