#include <iostream>
#include <cstdio>

using namespace std;

typedef long long LL;

const int N = 100010;
const LL INF = 9e18;

LL sum, f[N], mi, ans;
int n, c[N], d[N];

int main() {
    // freopen("shopping.in", "r", stdin);
    // freopen("shopping.out", "w", stdout);

    scanf("%d", &n);
    for (int i = 1; i <= n; ++i) scanf("%d%d", &c[i], &d[i]);

    mi = ans = INF;
    for (int i = 1; i <= n; ++i) {
        sum += c[i] + d[i];
        mi = min(mi, f[i - 1] - d[i]);
        ans = min(ans, mi + c[i]);
        f[i] = ans;
    }

    printf("%lld\n", ans + sum);

    return 0;
}