#include <cstdio>

 #include <algorithm>

 #include <cstring>

 #include <queue>

 using namespace std;

 const int maxn = 1e4+;

 const int INF = 0x3f3f3f3f;

 int N,len,a[maxn],b[maxn],save[];;

 struct node

 {

     int a,b,id;

     node(){}

     node(int x,int y,int z):a(x),b(y),id(z){}

     bool operator < (const node &b) const

     {

         return a<b.a;

     }

 }Dish[maxn];

 struct node2

 {

     int ed,id;

     node2(int x,int y):ed(x),id(y){}

     bool operator < (const node2 &b) const

     {

         return ed > b.ed;

     }

 };

 int solve(int ll,int rr)

 {

     int mid = (ll+rr)>>,cnt=;

     if(ll+ >= rr) return mid;

     priority_queue<node2> q;

     memset(save,,sizeof save);

     //printf("ll:%d rr:%d\n",ll,rr);

     for(int cur=;cur<=len;cur++)

     {

         //printf("cur:%d cnt:%d num:%d\n",cur,cnt,q.size());

         while(cnt < N && Dish[cnt].a == cur)

         {

              q.push(node2(Dish[cnt].b,Dish[cnt].id));

              cnt++;

         }

         //printf("save:%d mid:%d\n",save[q.top().id],mid);

         while(!q.empty() && save[q.top().id]>=mid && save[q.top().id])

         {

             q.pop();

         }

         if(!q.empty())   {/*printf("id:%d++\n",q.top().id);*/save[q.top().id]++;}

         while(!q.empty() && q.top().ed <= cur+)

         {

             if(save[q.top().id] < mid || save[q.top().id]==) {/*printf("id:%d save:%d\n",q.top().id,save[q.top().id]);*/return solve(ll,mid==?:mid);}

             q.pop();

         }

         if(q.empty()&&cnt==N) return solve(mid,rr);

     }

 }

 int main()

 {

     scanf("%d",&N);

     int l = INF,r = -INF;

     len = -INF;

     for(int i=;i<N;i++)

     {

         scanf("%d%d",&a[i],&b[i]);

         Dish[i] = node(a[i],b[i],i);

         r = max(b[i]-a[i],r);

         len = max(len,b[i]);

     }

     sort(Dish,Dish+N);

     printf("%d\n",solve(,r+)*N);

 }