#include <iostream> #include <iomanip> #include <cmath> double a[1002],b[1002]; using namespace std; int main() { bool tan = 1; int n; cin>>n; for(int i = 1;i <= n;i++) { cin>>a[i]>>b[i]; if(b[i]>a[i]) { tan = false;//cout<<"error"; //return 0; } if(a[i]<=0||b[i]<=0) { tan = false;//cout<<"error"; //return 0; } } double x,y; cin>>x>>y; if(x<=0||y<=0) { tan = false;//cout<<"error"; //return 0; } if(y>x) { tan = false;//cout<<"error"; //return 0; } //error判断； if(tan == 0) { cout<<"error"; return 0; } else { double sum1 = 0; for(int i = 1;i <= n;i++) { sum1+=a[i]; } if(sum1>=x) { sum1-=y; } else{sum1 = sum1;}//满减 double sum2 = 0; for(int i = 1;i <= n;i++) { sum2+=b[i]; } double fi = min(sum1,sum2); cout<<fixed<<setprecision(2)<<fi; } return 0; }