#include <iostream>
#include <cstdio>
#include <cstring>
#define pb push_back
#define mp make_pair
#define fi first
#define se second

typedef long long LL;

using namespace std;

template <typename T> void inline chkMax(T &x, T y) { if (y > x) x = y; }
template <typename T> void inline chkMin(T &x, T y) { if (y < x) x = y; }


template <typename T> void inline read(T &x) {
    int f = 1; x = 0; char s = getchar();
    while (s < '0' || s > '9') { if (s == '-') f = -1; s = getchar(); }
    while (s <= '9' && s >= '0') x = x * 10 + (s ^ 48), s = getchar();
    x *= f;
}

template <typename T> void print(T x) {
	if (x < 0) { putchar('-'); print(x); return ; }
    if (x >= 10) print(x / 10);
    putchar((x % 10) + '0');
}

const int N = 2005, S = 2000;

int n, a[N], b[N], f[N << 1], g[N << 1];

int main() {
	memset(f, 0xcf, sizeof f);
	read(n);
	for (int i = 1; i <= n; i++) {
		read(a[i]), read(b[i]);
	}
	f[S + 1] = 0;
	for (int i = 1; i <= n; i++) {
		int t = a[i] - 1;
		for (int j = S - n; j <= n + S; j++) g[j] = f[j];
		for (int j = S - n; j <= n + S; j++) {
			int ne = min(j + t, n + S);
			if (ne < S - n || ne > S + n) continue;
			chkMax(f[ne], g[j] + b[i]);
		}
	}
	int ans = 0;
	for (int i = S; i <= S + n; i++) chkMax(ans, f[i]);
	printf("%d\n", ans);
}