#include <fstream>
#include <cmath>

using namespace std;

ifstream fin("bilute.in");
ofstream fout("bilute.out");

int v[30005], nr[30005];

int main()
{
    int n;
    fin >> n;

    int maxx = 0, ind = -1;
    for(int i = 1; i <= n; ++i)
    {
        int l;
        fin >> nr[i] >> l;

        v[i] = nr[i] * l;
        if(v[i] > maxx)
        {
            maxx = v[i];
            ind = i;
        }
    }

    int time = 0;
    for(int i = 1; i <= n; ++i)
    {
        if(i != ind)
        {
            time += v[i];
            time += nr[i] * abs(i - ind);
        }
    }
    fout << time << '\n';
    return 0;
}