#include<bits/stdc++.h>
#define ll long long
#define pii pair<ll,ll>
#define lowbit(x) (x&-x)
#define log(x) (31^__builtin_clz(x))
using namespace std;
const int maxn=1e5+5;
ll hp[maxn];
ll h[maxn],at[maxn];
ll dis[maxn];
struct node{
    int v;
    ll w;
};
vector<node>e[maxn];
void solve(){
    ll n,t,mx=0;
    cin>>n>>t;
    mx=t;
    memset(hp,0x3f,sizeof(hp));
    memset(dis,0x3f,sizeof(dis));
    for(int i=1;i<=n;i++){
        ll t;
        cin>>t>>h[i];
        at[i]=t;
        mx=max(mx,t);
        hp[t]=min(hp[t],h[i]);
    }
    for(int i=1;i<=1e5;i++){
        e[i].push_back({i-1,0});
        if(hp[i]>1e5)continue;
        for(int l=1,r=1;l<hp[i];l=r+1){
            r=(hp[i]-1)/((hp[i]-1)/l);
            e[l].push_back({i,1ll*((hp[i]-1)/l-(hp[i]-1)/mx)*i});
        }
        
        // for(int j=1;(j)*(j)<=hp[i];j++){
        //     e[j].push_back({i,1ll*((hp[i]-1)/j-((hp[i]-1)/mx))*i});
        //     e[(hp[i]-1)/j+1].push_back({i,1ll*(j-1-((hp[i]-1)/mx))*i});
        // }
    }
    priority_queue<pii,vector<pii>,greater<pii>>q;
    q.push({0,t});
    dis[t]=0;
    while(!q.empty()){
        int u=q.top().second;
        ll d=q.top().first;
        q.pop();
        if(dis[u]<d)continue;
        for(auto t:e[u]){
            if(t.w<0)assert(0);
            if(dis[t.v]>t.w+dis[u]){
                dis[t.v]=t.w+dis[u];
                q.push({t.w+dis[u],t.v});
            }
        }
    }
    ll ans=dis[mx];
    // for(int i=1;i<=5;i++)cout<<dis[i]<<"\n";
    for(int i=1;i<=n;i++)ans=ans+1ll*((h[i]-1)/mx)*at[i];
    cout<<ans<<"\n";
}
int main(){
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t=1;
    // cin>>t;
    while(t--)solve();
    return 0;
}
/*


40 467
143 18391
471 22687
231 21806
383 94823
362 46527
451 88115
320 89601
360 92308
383 46466
349 95722
270 60335
126 36990
113 68071
355 58054
203 30398
394 36124
117 17117
269 29509
474 36595
201 70286
167 16541
495 63496
242 75553
235 39044
251 14389
212 10259
351 89496
439 83002
407 26598
280 56999
355 46834
174 98959
309 52220
455 30279
352 47589
130 69369
348 31572
423 52546
481 45063
109 54526
*/