/**
* Solution to IOI 2009 problem "area"
*
* Carl Hultquist, chultquist@gmail.com
*/
#include
using namespace std;
int main()
{
int n;
cin >> n;
// Be sure to use a 64-bit data-type here, as the answer could get
// very big!
long long area = 0;
for (int i = 0; i < n; i++)
{
// For safety, read in the sides of the property as 64-bit types
// too. This way, we know that the compiler won't try to do any
// operations in 32-bit.
long long a, b;
cin >> a >> b;
// Add on the area of this property to the total area
area += (a * b);
}
cout << area << endl;
return 0;
}