using namespace std;
int main(){
    freopen("super.in", "r", stdin);
    freopen("super.out", "w", stdout);
    int n;
    cin >> n;
    double a,b,c = 0;
    for (int i = 0;i < n;i++){
        scanf("%lf*%lf",&a,&b);
        c += a * b;
    }
    printf("%.2f\n",c);
    return 0;
}