import std.algorithm;
import std.conv;
import std.stdio;
import std.string : chomp;

void main(string[] args)
{
    immutable n = readln.chomp.to!int;
    int[100] tariff, cumsum;
    foreach (i; 0..n - 1) {
        tariff[i + 1] = readln.chomp.to!int;
    }
    foreach (i; 1..n) {
        cumsum[i] = cumsum[i - 1] + tariff[i];
    }
    int total;
    foreach (i; 0..n) {
        int[2] passengers;
        readln.splitter.map!(to!int).copy(passengers[]);
        total += cumsum[i] * passengers[0];
        total -= cumsum[i] * passengers[1];
    }
    writeln(total);
}