#include <cstdio>
#include <cstring>
#include <algorithm>
#define M 100002
#define INF 0x3f3f3f3f
using namespace std;

FILE * is = fopen("energii.in", "r");
FILE * os = fopen("energii.in", "w");

int n, w, e, c, s;
int mn = INF;
int d[M]; // d[i] =  costul minim pt cantitatea i de energie

int main()
{
    fscanf(os, "%d%d", &n, &w );
    memset(d, 63, sizeof(d));
    d[0] = 0;
    for ( int i = 1; i <= n; ++i )
    {
        fscanf(os, "%d%d", &e, &c );
        s += e;
        for ( int j = s-e; j >= 0; --j )
            if ( d[j+e] > d[j] + c )
                d[j+e] = d[j] + c;
    }
    for ( int i = w; i < s; ++i )
        mn = min(mn, d[i] );
    fprintf(os, "%d", mn );
    fclose(is);
    fclose(os);
    return 0;
}