#include<bits/stdc++.h>
using namespace std;
int n;
long long s,p[100005],c[100005];
long long sum;
int main(){
	scanf("%d %lld",&n,&s);
	long long res1=0,mn=INT_MAX;
	for(int i=1;i<=n;++i) scanf("%lld %lld",p+i,c+i),res1+=p[i],mn=min(mn,c[i]);
	res1=min(res1,s);
	sum+=mn*res1;
	for(int i=1;i<=n;++i) sum+=p[i]*(c[i]-mn);
	printf("%lld",sum);
}