#include <bits/stdc++.h>
//#pragma GCC optimize ("03")
#define FastIO ios_base::sync_with_stdio(false) , cin.tie(0) , cout.tie(0)
#define FILES freopen("energii.in" , "r" , stdin) , freopen("energii.out" , "w" , stdout)
#define ll long long
#define ull unsigned long long
#define ld long double
#define eb emplace_back
#define pb push_back
#define qwerty1 first
#define qwerty2 second
#define qwerty3 -> first
#define qwerty4 -> second
#define umap unordered_map
#define uset unordered_set
#define pii pair < ll , ll >
#define pq priority_queue
#define dbg(x) cerr << #x << ": " << x << '\n'

namespace FastRead
{
    char __buff[5000];ll __lg = 0 , __p = 0;
    char nc()
    {
        if(__lg == __p){__lg = fread(__buff , 1 , 5000 , stdin);__p = 0;if(!__lg) return EOF;}
        return __buff[__p++];
    }
    template<class T>void read(T&__x)
    {
        T __sgn = 1; char __c;while(!isdigit(__c = nc()))if(__c == '-')__sgn = -1;
        __x = __c - '0';while(isdigit(__c = nc()))__x = __x * 10 + __c - '0';__x *= __sgn;
    }
}

using namespace FastRead;
using namespace std;

const ll N = 5e3 + 10;
const ll M = 1e9 + 7;
const ld PI = acos(-1);
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int G , W;
int dp[N];

signed main()
{
	#ifndef ONLINE_JUDGE
		FastIO , FILES;
	#endif

	cin >> G >> W;

    for(int i = 0 ; i <= W ; i++)
        dp[i] = INT_MAX;

    dp[0] = 0;

    for(int i = 1 ; i <= G ; i++)
    {
        int e , c;
        cin >> e >> c;

        for(int g = W - e ; g < W ; g++)
            if(dp[g] != INT_MAX)
                dp[W] = min(dp[W] , dp[g] + c);

        for(int g = W - 1 ; g >= e ; g--)
            if(dp[g - e] != INT_MAX)
                dp[g] = min(dp[g] , dp[g - e] + c);
    }

    if(dp[W] == INT_MAX) cout << -1;
    else cout << dp[W];

    return 0;
}