#include <bits/stdc++.h>

using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");

int n, w;
long long c[1001], v[1001];
int cmin = 0x3f3f3f3f;

int main()
{
    fin >> n >> w;
    for(int i = 1; i <= n; ++i)
    {
        fin >> v[i] >> c[i];
        v[i] += v[i - 1];
        c[i] += c[i - 1];
    }
    if(w > v[n]) fout << -1;
    else
    {
        for(int i = 1; i < n; ++i)
            for(int j = i + 1; j <= n; ++j)
                if(v[j] - v[i] >= w and cmin > c[j] - c[i])
                    cmin = c[j] - c[i];
        fout << cmin;
    }
}