#include<set>
#include<map>
#include<cmath>
#include<ctime>
#include<stack>
#include<queue>
#include<deque>
#include<string>
#include<bitset>
#include<vector>
#include<cstdio>
#include<random>
#include<complex>
#include<cstdlib>
#include<climits>
#include<iomanip>
#include<cstring>
#include<cassert>
#include<stdlib.h>
#include<iostream>
#include<algorithm>
#include<unordered_map>
using namespace std;
// #define getchar()(p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++)
// char buf[1<<21],*p1=buf,*p2=buf;
const long long _base=107374183;
int writetemp[30];
inline int read()
{
    char c=getchar();int x=0;bool f=0;
    for(;!isdigit(c);c=getchar())f^=!(c^45);
    for(;isdigit(c);c=getchar())x=(x<<1)+(x<<3)+(c^48);
    if(f)x=-x;
    return x;
}
inline void write(unsigned long long x)
{
    int tot=(x==0);
    writetemp[1]=0;
    while(x) writetemp[++tot]=x%10,x/=10;
    while(tot) putchar(writetemp[tot--]+'0');
    putchar('\n');
    return ;
}
int n,m;
int deg[1000010];
int a[1000010];
int max1[1000010],max2[1000010];
int main()
{
    // freopen("s.out","r",stdin);
    // freopen("a.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++) scanf("%d",&a[i]);
    for(int i=1;i<=m;i++)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        deg[x]++,deg[y]++;
        if(a[y]>max1[x]) max2[x]=max1[x],max1[x]=a[y];
        else if(a[y]>max2[x]) max2[x]=a[y];
        swap(x,y);
        if(a[y]>max1[x]) max2[x]=max1[x],max1[x]=a[y];
        else if(a[y]>max2[x]) max2[x]=a[y];
    }
    int ans=0;
    for(int i=1;i<=n;i++) if(deg[i]!=1) ans=max(ans,a[i]);
    for(int i=1;i<=n;i++) ans=max(ans,max2[i]);
    printf("%d\n",ans);
    return 0;
}
/*
*/