poj 2393

贪心。

代码：

#include<iostream>
#include<fstream>

using namespace std;
long long n;

void read(){
//	ifstream cin("in.txt");
	long long i,j,k,s,t,minn;
	long long ans=0;
	cin>>n>>k;
	cin>>s>>t;
	ans=s*t;
	minn=s;
	for(i=1;i<n;i++)
	{
		cin>>s>>t;
		minn=min(minn+k,s);
		ans+=minn*t;
	}
	cout<<ans<<endl;
}

int main(){
	read();
	return 0;
}