#include<bits/stdc++.h>
using namespace std;
int v,n,c,k,m,sum,ans;
int main()
{
	cin>>v>>n>>c;
	for (int i=1;i<=n;++i)
	{
		cin>>k>>m;
		v-=k;
		c-=m;
	}
	if (c>=0) cout<<c<<endl;
	else cout<<"Impossible"<<endl;
	return 0;
}