(简单模拟2.1.1)POJ 2017 Speed Limit(跨项累加sumLen += (t2-t1)*v )

/* 
 * POJ_2017.cpp 
 * 
 *  Created on: 2013年10月24日 
 *      Author: Administrator 
 */  
#include   
#include   
  
using namespace std;  
  
int main() {  
    int n;  
  
  
    while (scanf("%d", &n) != EOF, n != -1) {  
        int t1 = 0, t2 = 0, v = 0;  
        int sumLen = 0;  
        int i;  
        for (i = 0; i < n; ++i) {  
            t1 = t2;  
            scanf("%d%d", &v, &t2);  
            sumLen += (t2 - t1) * v;  
        }  
  
        printf("%d miles\n",sumLen);  
    }  
  
    return 0;  
  
}