#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");

int n,c,dp[2][5005],w[1005],p[1005];

void citire()
{
    in>>n>>c;
    for(int i=1;i<=n;i++)
    {
        in>>w[i]>>p[i];
    }
}
void dinamica()
{
    memset(dp,0x3f,sizeof(dp));
    for(int i=1;i<=n;i++)
    {
        for(int j=0;j<=c;j++)
        {
            if(j-w[i]>0)
                dp[i%2][j]=min(dp[(i-1)%2][j],dp[(i-1)%2][j-w[i]]+p[i]);
            else
                dp[i%2][j]=min(dp[(i-1)%2][j],p[i]);
        }
    }
    if(dp[n%2][c]!=INF)
        out<<dp[n%2][c];
    else
        out<<-1;
}
int main()
{
    citire();
    dinamica();
    return 0;
}