#include <fstream>
#include <string>
#include <stdio.h>
#include <vector>
#include <algorithm>
#include <math.h>
#include <set>
#include <map>
#include <string.h>
#include <queue>
#include <stack>

#define INF 0x3f3f3f3f

using namespace std;

#ifdef DEBUG
string name = "data";
#else
string name = "energii";
#endif

ifstream fin(name + ".in");
ofstream fout(name + ".out");

#define MAXN 1024
#define MAXW 5001

int n, w;

int v[MAXN];
int c[MAXN];
int best[MAXN];
int p[MAXN];

int main() {
    
    fin >> n >> w;
    
    memset(best, 0x3f, sizeof(best));
    memset(p, 0x3f, sizeof(p));
    
    for (int i = 0 ; i < n ; ++i) {
        fin >> v[i];
        fin >> c[i];
    }
    
    for (int i = 0; i < n; ++i) {
        int key = min(w, v[i]);
        
        best[key] = min(best[key], c[i]);
        p[key] = i;
        
        for (int j = 0; j <= w; ++j) {
            if (best[j] != INF && p[j] != i) {
                int key = min(w, j + v[i]);
                best[key] = min(best[key], best[j] + c[j]);
            }
        }
    }
    
    if (best[w] != INF) {
        fout << best[w];
    } else {
        fout << -1;
    }

    return 0;
}