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

int bag,n,c,w[10100],v[10100],dp[1001][7000];

int check(int index,int rest,int step)
{
	if(dp[index][rest]!=-1)
	return dp[index][rest];
	int ans=0;
    if(rest<0)
       ans = step-1;
       else
    if(index==n+1)
        ans = 0;
        else{
    int p1 = check(index+1,rest,step);
    int p2=0;
    int next=check(index+1,rest-w[index],step+1);
    if(next!=step)
    p2=next+v[index];
    ans = step;
}
	dp[index][rest] = ans;
	return ans;
//    cout<<step<<endl;
}

int main()
{
    cin>>bag>>n>>c;
    int sum=0,flag=0,summ=0;
    for(int i=1;i<=n;i++)
    {
        cin>>w[i]>>v[i];
        sum+=w[i];
        if(v[i]<=c)
        {
        	flag=1;
        	summ+=w[i];
		}
    }
    if(sum<bag||(flag==0)||summ<bag)
        cout<<"Impossible";
    else cout<<check(1,bag,0);
    return 0;
}