rt.

#include <cstdio>
#include <cstring>
#include <algorithm>
#define GXR(i,j) f[(i)%2][j+O]
using namespace std;

const int O = 1e5+32; 
// 避免负数下标产生奇奇怪怪的问题

int f[2][O<<1],w[105],c[105];


int main() {
  int n; scanf("%d",&n);
  for (int i = 1; i <= n; i++) {
    int a,b; scanf("%d%d",&a,&b);
    w[i] = a+b; c[i] = a-b;
  }
  memset(f,-1,sizeof f);
  GXR(0,0) = 0; int ans = 0;
  for (int i = 1; i <= n; i++) {
    for (int j = O-520; j >= 520-O; j--) {
      //printf("%d chao.\n",j);
      if (GXR(i-1,j-c[i]) != -1) {
        GXR(i,j) = max(GXR(i,j),GXR(i-1,j-c[i])+w[i]);
      } 
    }
    ans = max(ans,GXR(i,0));
    for (int j = O-520; j >= 520-O; j--) {
      //printf("%d chao.\n",j);
      GXR(i+1,j) = GXR(i,j);
    }
  }
  printf("%d",ans);
  return 0;
}