#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 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;
}