#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")

#define rd_init() char*rp=({char*mmap();mmap(0l,1l<<25,1,2,0,0ll);})
#define rd() ({int _v=0,_c;while(_c=*rp++-48,_c>=0)_v=_v*10+_c;_v;})
#define wt(v) ({ulong _z=v;do*--wp=_z%10+48;while(_z/=10);})
#define wt1(v) ({char wbuf[64],*wp=wbuf+sizeof wbuf;wt(v);write(1,wp,wbuf+sizeof wbuf-wp);})
#define rep(v,e) for(typeof(e)v=0;v<e;++v)
#define reps(v,s,e) for(typeof(e)v=s;v<e;++v)
#define rrep(v,e) for(typeof(e)v=e;v--;)
#define max(a,b) (a>=b?a:b)

typedef unsigned long ulong;

long a[5000],b[5000];
long d[5001];
int main(){
	rd_init();
	int n=rd();
	rep(i,n){
		a[i]=rd();
		b[i]=rd();
	}
	rrep(i,n){
		long c=0;
		reps(j,i,n-1){
			c+=a[i];
			d[j]=max(d[j]+b[i],d[j+1]+c);
		}
		d[n-1]=d[n-1]+b[i];
	}
	long z=0;
	rep(i,n){
		z=max(z,d[i]);
	}
	wt1(z);
	_exit(0);
}