#include <bits/stdc++.h> using namespace std; int main() { int n; double a[1005],b[1005],sum1=0.0,sum2=0.0,c,d; bool t=0; cin >> n; for (int i=1;i<=n;i++) { cin >> a[i] >> b[i]; if (b[i]>a[i]) { t=1; } sum1+=b[i]; sum2+=a[i]; } cin >> c >> d; if (sum2>=c) { sum2-=d; } if (t==1||d>c) { cout << "error" << endl; return 0; } cout << fixed << setprecision(2) << min(sum1,sum2); return 0; }