#include <iostream>

using namespace std;

int n;
long long sum=0;

int relu(int m){
    if(m>0) return m;
    else return 0;
}


int main(){
    cin>>n; 
    for (int i = 0;i<n;i++){
        int w,x;
        cin>>w>>x;
        sum += w*x;
    } 
    sum = relu(sum);
    cout<<sum<<endl;

    return 0;
}