#include <bits/stdc++.h>
using namespace std;
const long long inf = 1LL << 60;
int a[500008], b[500008], c[500008], d[500008];
long long cost[500008];
long long dp[2][30008];
signed main() {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
int n; cin >> n;
long long A = 0, B = 0, ans = 0;
for (int i = 1; i <= n; ++i) cin >> a[i] >> b[i], A += a[i], B += b[i], c[i] = a[i], d[i] = b[i];
if (A == B) {
int pt1 = 1, pt2 = 1, trans;
while (pt2 <= n) {
if (!a[pt1]) ++pt1;
else if (!b[pt2]) ++pt2;
else {
trans = min(a[pt1], b[pt2]);
a[pt1] -= trans; b[pt2] -= trans;
ans += 1LL * trans * abs(pt1 - pt2);
}
}
cout << ans;
}
else if (A == B + 1) {
int pt = n, trans; ans = inf; long long cur = 0;
for (int i = n; i; --i) {
cost[i] = cost[i + 1];
while (c[i]) {
trans = min(c[i], d[pt]);
c[i] -= trans; d[pt] -= trans; cost[i] += 1LL * trans * abs(i - pt);
if (!c[i]) break;
--pt;
}
}
pt = 1;
for (int i = 1; i <= n; ++i) if (a[i]) {
while (a[i] && pt <= n) {
trans = min(a[i], b[pt]);
a[i] -= trans; b[pt] -= trans; cur += 1LL * trans * abs(i - pt);
if (!a[i]) break;
++pt;
}
if (pt <= n) ans = min(ans, cur - abs(i - pt) + cost[i + 1]);
else ans = min(ans, cur);
}
cout << ans;
}
else {
}
}
