#include <bits/stdc++.h>

using namespace std;
ifstream f ("energii.in");
ofstream g ("energii.out");
int n,energ;
int dp[2][10005];
int main()
{
    f>>n>>energ;
    for(int i=0;i<=1;++i)
        for(int j=1;j<=energ;++j)
            dp[i][j]=1000000;
    for(int i=1; i<=n; ++i)
    {
        int e,cost;
        f>>e>>cost;
        for(int j=1; j<=energ; ++j)
        {
            if(j >= e)
                dp[i%2][j]=min(dp[(i-1)%2][j],dp[(i-1)%2][j-e]+cost);
            else
                dp[i % 2][j]=min(dp[(i-1)%2][j],cost);

        }
    }
    if(dp[n%2][energ]==1000000)
        g<<-1;
    else
        g << dp[n % 2][energ];
    return 0;
}