#include <iostream>
#include <vector>
#include <queue>

using namespace std;

#define mp make_pair
#define pb push_back

const long long INF = 1e9;

int main()
{
#ifdef _DEBUG
    freopen("in.txt", "r", stdin);
    freopen("out.txt", "w", stdout);
#endif
    long long n; scanf("%I64d", &n);
    vector<long long> t(n), c(n);
    for(long long i = 0; i < n; i++)
        scanf("%I64d%I64d", &t[i], &c[i]);

    vector<vector<long long>> z(n + 1, vector<long long>(4001, INF));

    z[1][1999] = 0;
    z[1][2000 + t[0]] = c[0];
    for(long long i = 1; i < n; i++){
        for(long long j = 0; j <= 4000; j++){
            if(z[i][j] != INF){
                if(j > 0)
                    z[i + 1][j - 1] = min(z[i + 1][j - 1], z[i][j]);
                z[i + 1][min(4000LL, j + t[i])] = min(z[i + 1][min(4000LL, j + t[i])], z[i][j] + c[i]);
            }
        }
    }
    long long res = INF;
    for(long long i = 2000; i <= 4000; i++)
        if(z[n][i] < res){
            res = z[n][i];
        }
    cout << res << endl;

    return 0;
}