#include<cstdio>
#include<vector>
#include<algorithm>
long long a[100005], b[100005];
long long c[100005];
int order[100005];
long long sum[100005], p[100005];
std::vector<int>g[100005];
std::vector<int>e[100005];
int vis[100005];
long long f[100005];

long long min(long long a,long long b){ return a>b?b:a; }

long long max(long long a,long long b){ return a>b?a:b; }

int find(int u){
    if(p[u]==u) return u;
    else return p[u] = find(p[u]);
}

void dp(int u){
    sum[u] = b[u];
    for(int v: e[u]){
        dp(v);
        sum[u] += sum[v];
    }
    f[u] = c[u]+sum[u];
    for(int v: e[u]){
        f[u] = min(f[u],max(f[v],c[u])+sum[u]-sum[v]);
    }
}

int cmp(int a,int b){ return c[a]<c[b]; }

int main(){
    int n,m;
    scanf("%d%d",&n,&m);
    for(int i = 1; i <= n; i++){
        order[i] = p[i] = i;
        sum[i] = 0;
        scanf("%lld%lld",&a[i],&b[i]);
        c[i] = a[i]-b[i];
        if(c[i]<0) c[i] = 0;
    }
    for(int i = 0; i < m; i++){
        int u,v;
        scanf("%d%d",&u,&v);
        g[u].push_back(v);
        g[v].push_back(u);
    }
    std::sort(order+1,order+1+n,cmp);
    for(int i = 1; i <= n; i++){
        int u = order[i]; 
        vis[u] = 1;
        for(int v: g[u]){
            if(vis[v] && find(v)!=u){
                int root = find(v);
                p[root] = u;
                //sum[u] += sum[root];
                e[u].push_back(root);
            }
        }
    }
    //printf("ok\n");
    int root = find(1);
    dp(root);
    printf("%lld\n",f[root]);
    return 0;
}
