#include <stdio.h>
#define MAX_G 5000
#define MAX_COST 10000000

int d[MAX_G + 1];

int main() {
    FILE *fin, *fout;
    int n, g, e, c, i, j;

    fin = fopen( "energii.in", "r" );
    fscanf( fin, "%d%d", &n, &g );
    for ( i = 1; i <= g; i++ )
        d[i] = MAX_COST;
    for ( i = 0; i < n; i++ ) {
        fscanf( fin, "%d%d", &e, &c );
        for ( j = g; j >= e; j-- )
            d[j] = d[j - e] + c < d[j] ? d[j - e] + c : d[j];
        for ( j = e - 1; j >= 0; j-- )
            d[j] = d[j] < c ? d[j] : c;
    }
    fclose( fin );

    fout = fopen( "energii.out", "w" );
    fprintf( fout, "%d", d[g] == MAX_COST ? -1 : d[g] );
    fclose( fout );

    return 0;
}