LG5244

#include<bits/stdc++.h>

using namespace std;

#define gc c=getchar()
#define r(x) read(x)
#define ll long long

template<typename T>
inline void read(T&x){
    x=0;T k=1;char gc;
    while(!isdigit(c)){if(c=='-')k=-1;gc;}
    while(isdigit(c)){x=x*10+c-'0';gc;}x*=k;
}

const int N=2e5+7;
const int V=1e6+7;
const ll INF=1e18;

struct Point{
    int x,y;
    inline bool operator <(const Point &a)const{
        return x==a.x?y<a.y:x<a.x;
    }
}P[N];

int c[V];

inline void Add(int x,int v){
    for(int i=x;i<V;i+=(i&-i)){
        c[i]=max(c[i],v);
    }
}

inline int Max(int x){
    int ret=0;
    for(int i=x;i;i^=(i&-i)){
        ret=max(ret,c[i]);
    }
    return ret;
}

#define ls (rt<<1)
#define rs (rt<<1|1)

vector<int>Q[N<<2];

void build(int rt,int l,int r){
    Q[rt].clear();
    if(l==r)return ;
    int mid=(l+r)>>1;
    build(ls,l,mid);
    build(rs,mid+1,r);
}

void insert(int rt,int l,int r,int x,int y,int v){
    if(x<=l&&r<=y){
        Q[rt].push_back(v);
        return ;
    }
    int mid=(l+r)>>1;
    if(x<=mid)insert(ls,l,mid,x,y,v);
    if(y>mid)insert(rs,mid+1,r,x,y,v);
}

vector<int>group[N];
vector<ll>dp[N];

void solve(vector<int>&T,int l,int r,int x,int y,int id){
    if(l>r)return ;
    int mid=(l+r)>>1;
    ll ret=INF;
    int pos;
    Point A=P[group[id][T[mid]]];
    for(int i=x;i<=y;++i){
        Point B=P[group[id-1][i]];
        ll tmp=dp[id-1][i]+(ll)(A.x-B.x)*(A.y-B.y);
        if(ret>tmp)ret=tmp,pos=i;
    }
    dp[id][T[mid]]=min(dp[id][T[mid]],ret);
    solve(T,l,mid-1,pos,y,id);
    solve(T,mid+1,r,x,pos,id);
}

void dfs(int rt,int l,int r,int id){
    solve(Q[rt],0,Q[rt].size()-1,l,r,id);
    if(l==r)return;
    int mid=(l+r)>>1;
    dfs(ls,l,mid,id);
    dfs(rs,mid+1,r,id);
}

int f[N];

int main(){
    // freopen(".in","r",stdin);
    // freopen(".out","w",stdout);
    int n,T;r(n),r(T);
    for(int i=1;i<=n;++i){
        r(P[i].x),r(P[i].y);
    }
    sort(P+1,P+n+1);
    ++n;
    P[n].x=T;
    P[n].y=T;
    group[0].push_back(0);
    dp[0].push_back(0);
    for(int i=1;i<=n;++i){
        f[i]=Max(P[i].y)+1;
        group[f[i]].push_back(i);
        Add(P[i].y,f[i]);
    }
    for(int i=1;i<=f[n];++i){
        int m=group[i-1].size()-1;
        build(1,0,m);
        for(int j=0,l,r,mid,ans;j<group[i].size();++j){
            dp[i].push_back(INF);
            Point &A=P[group[i][j]];
            l=0,r=m;
            while(l<=r){
                mid=(l+r)>>1;
                if(P[group[i-1][mid]].y<=A.y)r=mid-1,ans=mid;
                else l=mid+1;
            }
            int st=ans;
            l=0,r=m;
            while(l<=r){
                mid=(l+r)>>1;
                if(P[group[i-1][mid]].x<=A.x)l=mid+1,ans=mid;
                else r=mid-1;
            }
            int ed=ans;
            insert(1,0,m,st,ed,j);
        }
        dfs(1,0,m,i);
    }
    printf("%lld\n",dp[f[n]][0]);
}