#include <stdio.h>

#define MAXN 5000
#define MAXG 10000

FILE *fin, *fout;

int g[MAXN+1];
int p[MAXN+1];
int v[MAXG+1];

int main() {
    int n, greutate, i, gg, suma, j;
    fin = fopen("energii.in", "r");
    fout = fopen("energii.out", "w");
    
    fscanf(fin, "%d%d", &n, &greutate);
    
    suma = 0;
    for (i=1; i<=n; i++) {
        fscanf(fin, "%d%d", &g[i], &p[i]);
        suma+=g[i];
    }
    
    for (i=1; i<=greutate; i++) {
        v[i] = 1000000000;
    }
    
    if (suma<greutate) {
        fprintf(fout, "%d", -1);
    } else {
    
        for (i=1; i<=n; i++) {
            for (gg=greutate; gg>=0; gg--) {
                j = g[i]+gg;
                if (j>greutate) {
                    j = greutate;
                }
                if (v[j] > v[gg]+p[i]) {
                    v[j] = v[gg]+p[i];
                }
            }
        }
        
        fprintf(fout, "%d\n", v[greutate]);
        
    }
    
    fclose(fin);
    fclose(fout);
    return 0;
}