1059A - Cashier

#include<bits/stdc++.h>

using namespace std;

int main()

{

    int L,n,a;

    int count=0,start=0;

    cin>>n>>L>>a;

    if(n>0)

    {

        int i=0,temp=0;;

        int ti,li;

        while(i<n)

        {

            int ti,li;

            cin>>ti>>li;

            if(start==0&& ti>a)

            {

                start=ti+li;

                count = ti/a;

            }

            else

            {

                if(ti-start>=a)

                {

                    int time= ((ti-start)/a);

                    start=ti+li;

                    count+=time;

                }

                else

                {

                    start=ti+li;

                }

            }

            i++;

        }

        if(L-start>=a)

        {

            int t=(L-start)/a;

            count+=t;

        }

        cout<<count<<endl;

    }

    else

    {

        cout<<L/a<<endl;

    }

}