poj2393

//连我都能ac的一道贪心题，记录一下

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
using namespace std;


int main(){
pair<int,int> a[10001];
int n,s,b,c,i,j;
while(cin>>n>>s){
for( i = 0;i<n;++i){
cin>>b>>c;
a[i].first = b;
a[i].second = c;
}
__int64 num = 0; 
for( i = 0;i<n;++i){
num += a[i].first*a[i].second;
for( j = i+1;j<n;++j){
if(a[j].first - a[i].first <= s*(j-i))
break;
else{
num += a[i].first*a[j].second+s*(j-i)*a[j].second;
a[j].second = 0;}
}
}
printf("%I64d\n",num);
}
return 0;
}