#include<bits/stdc++.h>
using namespace std;

void solve(){
    long long n,c;
    cin>>n>>c;
    
    multiset<array<long long,3>> opz; //passo,num,residuo
    multiset<array<long long,3>> curr; //tempo di fine,passo,residuo
    
    long long sum=0;
    for(int i=0;i<n;i++){
        long long t,d;
        cin>>t>>d;
        sum+=t;
        opz.insert({d,t/d,t%d});
    }
    
    long long ans=0,currt=0,currpasso=0;
    
    auto updcurr = [&](){
        while((int)curr.size()<c && opz.size()>0){
            auto x = *opz.rbegin();
            opz.erase(opz.find(x));
            
            currpasso+=x[0];
            swap(x[0],x[1]);
            x[0]+=currt;
            
            //cout<<"aggiungo "<<x[0]<<" "<<x[1]<<" "<<x[2]<<"\n";
            curr.insert(x);
        }
    };
    
    auto delcurr = [&](){
        while(!curr.empty() && (*curr.begin())[0]==currt){
            if((*curr.begin())[2]!=0){
                opz.insert({(*curr.begin())[2],1,0});
            }
            currpasso-=(*curr.begin())[1];
            curr.erase(curr.begin());
        }
    };
    
    updcurr();

    while(sum>c){
        long long succt=(*curr.begin())[0];
        
        long long tmp = min(succt-currt,(sum-c+currpasso-1)/currpasso);
        
        //cout<<"passa "<<tmp<<" secondi\n";
        ans+=tmp;
        currt+=tmp;
        sum-=tmp*currpasso;
        
        
        if(sum<=c){
            assert(tmp>=1);
            break;
        }
        delcurr();
        updcurr();
    }
    
    vector<long long> v;
    for(auto i : curr)v.push_back(i[1]);
    
    
    long long rim = c-v.size();
    
    if(ans>0){
        if(rim>=sum)ans--;
        else{
            sort(v.begin(),v.end());
            for(int i=0;i<(int)v.size();i++){
                rim++;
                sum+=v[i];
                if(rim>=sum){
                    ans--;
                    break;
                }
            }
        }
    }
    
    
    cout<<ans<<"\n";
}

int main(){
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    
    int t=1;
    //cin>>t;
    for(int i=1;i<=t;i++)solve();
    
    return 0;
}