#include <stdio.h>
#include <algorithm>
using namespace std;

struct generator {
    int energie;
    int cost;
    float raport;
};

generator generatoare[10001];
int vec[1000001];

bool cmp(generator a, generator b) { return a.energie > b.energie; }

int main()
{
    freopen("energii.in", "r", stdin);
    freopen("energii.out", "w", stdout);

    int g, w, i, energie_maxima = 0, cost_minim = 0, energie_minima = 0;
    scanf("%d%d", &g, &w);

    for(i = 1; i <= g; i++)
    {
            scanf("%d%d", &generatoare[i].energie, &generatoare[i].cost);
            energie_maxima += generatoare[i].energie;
    }
    if( energie_maxima > w ) printf("-1");
 /*       int j;
        for( i = 1; i <= g; i++ )
        {
            for(j=1000000;j>=1;j--) {
                if(vec[j] != 0)
                    vec[ j+generatoare[i].energie ] += generatoare[i].cost;
            }
            vec[generatoare[i].energie] += generatoare[i].cost;
        }

        for(i=1; i<=10000; i++) printf("%d ", vec[i]);*/

}