#include <bits/stdc++.h>
using namespace std;
using ll=long long;
#define P pair<int,int>
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<n;i++)
#define all(v) v.begin(),v.end()
#define pb push_back
template<class T,class U>
inline bool chmax(T &a,U b){
    if(a<b){
        a=b;
        return true;
    }
    return false;
}
template<class T,class U>
inline bool chmin(T &a,U b){
    if(a>b){
        a=b;
        return true;
    }
    return false;
}
constexpr int INF=1000000000;
constexpr ll llINF=1000000000000000000;
constexpr int mod=1000000007;
constexpr double eps=1e-8;
const double pi=acos(-1);
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
int Random(int mi,int ma){
    random_device rnd;
    mt19937 mt(rnd());//32bit
    //[mi,ma]
    uniform_int_distribution<int>engine(mi,ma);
    return engine(mt);
}
/*
vector<vector<ll>>C,sC;
void init_comb(int n,int m){
    C.resize(n+1,vector<ll>(m+1,0));
    sC.resize(n+1,vector<ll>(m+1,0));
    C[0][0]=1;
    for(int i=1;i<=n;i++){
        C[i][0]=1;
        for(int j=1;j<=m;j++){
            C[i][j]=(C[i-1][j-1]+C[i-1][j])%mod;
        }
    }
    rep(i,n+1){
        rep(j,m){
            sC[i][j+1]=(sC[i][j]+C[i][j])%mod;
        }
    }
}*/
ll gcd(ll a,ll b){
    while(a%b){
        a%=b;
        swap(a,b);
    }
    return b;
}
ll lcm(ll a,ll b){
    return a/gcd(a,b)*b;
}
bool prime(int a){
    if(a==1)return false;
    for(int i=2;i*i<=a;i++){
        if(a%i==0)return false;
    }
    return true;
}
ll modpow(ll a,ll b){
    ll res=1;
    while(b){
        if(b&1){
            res*=a;
            res%=mod;
        }
        a*=a;
        a%=mod;
        b>>=1;
    }
    return res;
}
vector<ll>inv,fact,factinv;
void init_fact(int n){
    inv.resize(n+1);
    fact.resize(n+1);
    factinv.resize(n+1);
    inv[0]=0;
    inv[1]=1;
    fact[0]=1;
    factinv[0]=1;
    for(ll i=1;i<=n;i++){
        if(i>=2)inv[i]=mod-((mod/i)*inv[mod%i]%mod);
        fact[i]=(fact[i-1]*i)%mod;
        factinv[i]=factinv[i-1]*inv[i]%mod;
    }
}
ll _inv(ll a,ll m=mod){
    //gcd(a,m) must be 1
    ll b=m,u=1,v=0;
    while(b){
        ll t=a/b;
        a-=t*b;swap(a,b);
        u-=t*v;swap(u,v);
    }
    u%=m;
    if(u<0)u+=m;
    return u;
}
ll comb(int a,int b){
    if(a<b)return 0;
    if(a<0)return 0;
    return fact[a]*factinv[a-b]%mod*factinv[b]%mod;
}
ll multicomb(int a,int b){
    return comb(a+b-1,b);
}

int dp[200010];
int main(){
    cin.tie(0);ios::sync_with_stdio(false);
    int n,m,a[200010];
    vector<int>g[200010];
    cin>>n>>m;
    rep(i,n){
        cin>>a[i];
        dp[i]=INF;
    }
    rep(i,m){
        int x,y;
        cin>>x>>y;
        x--,y--;
        g[x].pb(y);
    }
    int ans=-INF;
    rep(i,n){
        chmin(dp[i],a[i]);
        for(int j:g[i]){
            chmin(dp[j],dp[i]);
            chmax(ans,a[j]-dp[j]);
        }
    }
    cout<<ans<<endl;
    return 0;
}
#include <bits/stdc++.h>
#define ll long long
#define pii pair<int,int>
#define x first
#define y second
using namespace std;
int n,m,a[1001],b[1001],dp[1001][1001];
int main(){
cin>>n>>m;
for(int k=1;k<=n;k++){
    cin>>a[k];
    dp[k][0]=k;
}
for(int k=1;k<=m;k++){
    cin>>b[k];
    dp[0][k]=k;
}
if(a[1]!=b[1])
    dp[1][1]=1;
for(int k=1;k<=n;k++){
    for(int i=1;i<=m;i++){
        dp[k][i]=dp[k-1][i]+1;
        dp[k][i]=min(dp[k][i],dp[k][i-1]+1);
        int gt=dp[k-1][i-1];
        if(a[k]!=b[i])
            gt++;
            dp[k][i]=min(dp[k][i],gt);
    }
}
cout<<dp[n][m];
return 0;
}
