#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma optimize("unroll-loops")
#define fast ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define all(x) x.begin(), x.end()
#define rll(x) x.rbegin(), x.rend()
#define COMP(x) x.erase(unique(all(x)), x.end())
#define MOD 1000000007
#define MOD2 998244353
#define sz(x) (ll)x.size()
typedef __int128_t lll;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll,ll> pll;
typedef pair<ll, pll> PP;
const ll Lnf = 2e18;
ll n;
ll A[505050], B[505050];
int main(){
fast;
cin>>n;
ll ans = 0;
for(int i = 1 ; i <= n ; i++){
cin>>A[i]>>B[i];
A[i] += A[i-1];
B[i] += B[i-1];
ans += abs(A[i]-B[i]);
}
if(A[n]==B[n])return !(cout<<ans);
// cout<<ans<<endl;
ll t = ans;
for(int i = n ; i >= 1 ; i--){
t -= abs(A[i]-B[i]);
A[i]--;
t += abs(A[i]-B[i]);
ans = min(ans,t);
}
cout<<ans;
}
