#include<stdio.h>
#include<values.h>
#define MaxN 100
FILE*f=fopen("energii.in","r");
FILE*g=fopen("energii.out","w");
long cost[MaxN],c[MaxN],x[MaxN],y[MaxN];
int main()
	{
	long i,j,min,n,s;
	fscanf(f,"%ld %ld",&n,&s);
	for(i=1;i<=n;++i) fscanf(f,"%ld %ld",&c[i],&cost[i]);
	for(i=c[1]+1;i<=s;++i) x[i]=MAXLONG;
	for(i=1;i<=c[1];++i) x[i]=cost[1];
	for(i=2;i<=n;++i)
		{
		for(j=1;j<c[i];++j)
			{
			y[j]=x[j];
			if(cost[i]<y[j]) y[j]=cost[i];
			}
		for(j=c[i];j<=s;++j) y[j]=x[1]+cost[i];
		for(i=1;i<=s;++i) x[i]=y[i];
		}
	fprintf(g,"%ld",y[s]);
	return 0;
	}