#include <bits/stdc++.h>

using namespace std; const int maxn = 80; typedef long long ll;

int n, m;

ll a[maxn], b[maxn];

ll G[maxn];

map<ll, ll> mp;

inline bool ck(int u, int v)
{
    if ((a[u] - b[u] > 0) != (a[v] - b[v] > 0))
        return (a[u] - b[u] > 0) < (a[v] - b[v] > 0);
    if (a[u] - b[u] > 0) return a[u] < a[v]; return b[u] > b[v];
}

ll dfs(ll S, ll T, int lst)
{
    T &= ~S;
    if (T == 0) return 0;
    if (mp.count(S)) return mp[S];
    ll res = 1e18;
    for (int u = 1; u <= n; u++) if (T >> u & 1)
    {
        if (!lst || ck(lst, u) || (G[lst] >> u & 1))
        {
            ll tmp = dfs(S | (1ull << u), T | G[u], u);
            if (tmp >= b[u]) tmp += a[u] - b[u]; else tmp = a[u];
            res = min(res, tmp);
        }
    }
    return mp[S] = res;
}

int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 2; i <= n; i++) scanf("%lld%lld", a + i, b + i);
    for (int i = 1, u, v; i <= m; i++) scanf("%d%d", &u, &v), G[u] |= 1ull << v;
    printf("%lld\n", dfs(0, 1 << 1, 0));
    return 0;
}