#include<cmath> 
using namespace std;
int a[11000],b[110000];
int main()
{
	int v,n,c;
	cin>>v>>n>>c;
	for(int i=0;i<n;i++)
	{
		cin>>a[i]>>b[i];
		if(b[i]<=c && a[i]<=v)
		{
			c=c-b[i];
			v=v-a[i];
		}
	}
	if(v<=0)
	{
		cout<<c<<endl;
		return 0;
	}else 
	{
		cout<<"Impossible"<<endl;
		return 0;
	}
}