#include <bits/stdc++.h>
#define vi vector<int>
using ll=long long;
#define int ll
using namespace std;
int f(int k, vector<int>x, vector<int>y){
int n=x.size();
int u=0;
int d=k;
int ix=0;//index in x
int iy=0;//index in y
//remove k people
while(k){
if(y[iy]==0){
iy++;
continue;
}
int c=min(k,y[iy]);
k-=c;
y[iy]-=c;
}
//assign everyone in y to the lowest possible x
while(iy<n){
if(y[iy]==0){
iy++;
continue;
}
if(x[ix]==0){
ix++;
continue;
}
int c=min(x[ix],y[iy]);
x[ix]-=c;
y[iy]-=c;
if(ix>iy)d+=c;
if(ix<iy)u+=c;
}
return u-d;
}
inline int slope(int k, vector<int>&x,vector<int>&y){
return f(k+1,x,y)-f(k,x,y);
}
signed main() {
int n;
cin>>n;
vi x(n);
vi y(n);
for(int &i:x)cin>>i;
for(int &i:y)cin>>i;
int sum= accumulate(y.begin(),y.end(),0ll);
int l=0,r=sum;
while(r>l){
int m=(l+r)/2;
if(slope(m,x,y)<0)r=m;
else l=m+1;
}
int result=f(l,x,y);
cout<<result<<endl;
return 0;
}
