#include<cstdio>

 #include<algorithm>

 #include<cstring>

 #include<vector>

 using namespace std;

 #define fi first

 #define se second

 #define mp make_pair

 #define pb push_back

 typedef long long ll;

 typedef unsigned long long ull;

 typedef pair<int,int> pii;

 int n,c;

 int ans;

 pii t1[];

 int len;

 int main()

 {

     int t,i,x,y,s;

     bool fl;

     scanf("%d%d",&n,&c);

     for(i=;i<=n;i++)

     {

         scanf("%d%d",&x,&y);

         if(x>=c)    ans+=y;

         else    t1[++len]=mp(x,y);

     }

     sort(t1+,t1+len+);

     while()

     {

         fl=;

         for(i=;i<=len;i++)

             if(t1[i].se!=)

                 fl=;

         if(!fl)    break;

         s=;

         for(i=len;i>=;i--)

         {

             t=min(t1[i].se,(c-s)/t1[i].fi);

             s+=t1[i].fi*t;

             t1[i].se-=t;

         }

         if(s<c)

         {

             fl=;

             for(i=;i<=len;i++)

                 if(t1[i].se!=)

                     fl=;

             if(!fl)    break;

             for(i=;i<=len;i++)

                 if(t1[i].se)

                 {

                     --t1[i].se;

                     break;

                 }

         }

         ans++;

     }

     printf("%d",ans);

     return ;

 }