#include <stdio.h>struct player{int w,b;};int max(int a,int b){if (a>b) return a;else return b;}int f[1003][16][16]={0};main(){struct player a[1003];int l=0,x,y;while(scanf("%d%d",&x,&y)!=EOF){l++;a[l].w=x;a[l].b=y;}int i;f[1][1][0]=a[1].w;f[1][0][1]=a[1].b;for (i=2;i<=l;i++){int j,k;for (j=0;j<=15;j++){int t=(i-j)<15?(i-j):15;for (k=0;k<=t;k++) {if (j==0&&k==0) f[i][j][k]=0;else if (j==0)f[i][j][k]=max(f[i-1][j][k-1]+a[i].b,f[i-1][j][k]);else if (k==0)f[i][j][k]=max(f[i-1][j-1][k]+a[i].w,f[i-1][j][k]);elsef[i][j][k]=max(max(f[i-1][j-1][k]+a[i].w,f[i-1][j][k-1]+a[i].b),f[i-1][j][k]);}}}printf("%dn",f[l][15][15]);}
