#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
const int N = 5e5 + 5;
ll T[N];
ll Solve(int n)
{
multiset<ll> Left, Right;
ll level = 0;
ll offsetL = 0, offsetR = 0;
Left.insert(0);
Right.insert(0);
if(T[0] < 0) {
offsetL += T[0];
offsetR += T[0];
} else
offsetR += T[0];
for(int i = 1; i < n; i++) {
ll a = 0 - offsetL;
ll b = 0 - offsetR;
if(Left.empty()) {
if(b < *Right.begin()) {
level += (*Right.begin() - b);
Right.insert(*Right.begin());
} else {
if(b <= *(--Right.end())) {
Right.insert(b);
Right.insert(b);
}
Left.insert(*Right.begin() + offsetR - offsetL);
level += (b - *Right.begin());
Right.erase(Right.begin());
}
} else if(Right.empty()) {
if(a > *(--Left.end())) {
level += (a - *(--Left.end()));
Left.insert(*(--Left.end()));
} else {
if(a >= *Left.begin()) {
Left.insert(a);
Left.insert(a);
}
Right.insert(*(--Left.end()) + offsetL - offsetR);
level += (*(--Left.end()) - a);
Left.erase(--Left.end());
}
} else {
if(a >= *(--Left.end()) && b <= *Right.begin()) {
Left.insert(a);
Right.insert(b);
} else if(a < *(--Left.end())) {
if(a >= *Left.begin()) {
Left.insert(a);
Left.insert(a);
}
Right.insert(*(--Left.end()) + offsetL - offsetR);
level += (*(--Left.end()) - a);
Left.erase(--Left.end());
} else {
if(b <= *(--Right.end())) {
Right.insert(b);
Right.insert(b);
}
Left.insert(*Right.begin() + offsetR - offsetL);
level += (b - *Right.begin());
Right.erase(Right.begin());
}
}
if(T[i] < 0) {
offsetL += T[i];
offsetR += T[i];
} else
offsetR += T[i];
}
if(Right.empty())
return level;
ll val = level;
ll slope = 0;
ll last = 0;
for(auto e : Right) {
ll pos = e + offsetR;
val += (pos - last) * slope;
if(pos >= 0)
return val - pos*slope;
slope++;
last = pos;
}
return -1;
}
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(0);
int n, a, b;
cin >> n;
for(int i = 0; i < n; i++) {
cin >> a >> b;
T[i] = a - b;
}
cout << Solve(n) << "\n";
return 0;
}
