样例都对，就是测试的时候WA了......

#include <map>
#include <set>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <array>
#include <cstdio>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <iomanip>
#include <iterator>
#include <iostream>
#include <algorithm>

using namespace std;

typedef long long LL;

const int N = 2e3 + 5;
const int M = 4e3 + 5;
const int MOD = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const int NEG_INF = -0x3f3f3f3f;

LL n, v = 0, ans = INF, t[N], c[N], dp[M];

int main(void) {
	memset(dp, INF, sizeof(dp));
	dp[0] = 0;
	scanf("%lld", &n);
	for (LL i = 1; i <= n; ++i) {
		scanf("%lld%lld", &t[i], &c[i]);
		++t[i];
		v = max(v, t[i]);
	}
	v += n;
	for (LL i = 1; i <= n; ++i) {
		for (LL j = v; j >= t[i]; --j) {
			dp[j] = min(dp[j], dp[j - t[i]] + c[i]);
		}
	}
	for (LL i = n; i <= v; ++i) {
		ans = min(ans, dp[i]);
	}
	printf("%lld\n", ans);

	return 0;
}