#include <cstdio>
#include <algorithm>
using namespace std;
const int MAXN = 2010;
int N, A[MAXN], B[MAXN], dp[MAXN][2*MAXN+1];
int main()
{
scanf("%d", &N);
for(int i=0;i<N;i++) scanf("%d%d", A+i, B+i);
for(int i=0;i<=2*MAXN;i++) dp[0][i] = -2100000000;
dp[0][MAXN+1] = 0;
for(int i=0;i<N;i++){
for(int j=0;j<=2*MAXN;j++) dp[i+1][j] = -2100000000;
for(int j=0;j<=2*MAXN;j++){
int j2 = j + (A[i] - 1);
if(j2 < 0) continue;
if(j2 > 2*MAXN) j2 = 2*MAXN;
dp[i+1][j2] = max(dp[i+1][j2], dp[i][j] + B[i]);
dp[i+1][j] = max(dp[i+1][j], dp[i][j]);
}
}
int ret = 0;
for(int i=MAXN;i<=2*MAXN;i++) ret = max(ret, dp[N][i]);
printf("%d\n", ret);
return 0;
}
