20-12-01（期末预测之安全指数）

package csp;
import java.util.*;
public class csp_20_12_01 {
    
    
	
	public static void main(String[] args){
    
    
	  Scanner in = new Scanner(System.in);
	  int n = in.nextInt();
	  int result = 0;
	  
	for(int i =0;i<n;i++){
    
    
	 int score = in.nextInt();
	 int w = in.nextInt();
	 result += score*w;
	}//for

	 if(result>0){
    
    
	System.out.print(result);
	}else{
    
    
	System.out.print("0");
	}
	}//main

	
}