#include<iostream>
#include<cstdio>
using namespace std;
int main(){
    int n,sum,s[15],t[15];
    while(scanf("%d",&n)&&n!=-1){
        for(int i=1;i<=n;i++){
            scanf("%d%d",&s[i],&t[i]);
        }
        sum = 0;
        t[0] = 0;
        for(int i=1;i<=n;i++){
            sum += s[i]*(t[i]-t[i-1]);
        }
        printf("%d miles\n",sum);
    }
    return 0;
}