#include<cstdio>
#include<algorithm>

using namespace std;

const int nmax=1e5+5;

struct al
{
    int x,y;
}v[nmax];

long long d[nmax];

inline bool cmp(al a,al b)
{
    return a.y<b.y;
}

inline int bsearch(int x,int dr)
{
    int i,step=1<<20;
    for(i=1;step;step>>=1)
        if(i+step<dr && v[i+step].y <=x)
            i+=step;
    return i;
}

inline long long max(long long a,long long b)
{
    if(a>b)
        return a;
    return b;
}

int main()
{
    freopen("heavymetal.in","r",stdin);
    freopen("heavymetal.out","w",stdout);
    int n,i,j;
    scanf("%d",&n);
    for(i=1;i<=n;++i)
        scanf("%d%d",&v[i].x,&v[i].y);
    sort(v+1,v+n+1,cmp);
    d[1]=v[1].y-v[1].x;
    int poz;
    for(i=2;i<=n;++i)
    {
        poz=bsearch(v[i].x , i);
        d[i]=d[poz]+v[i].y-v[i].x;
        d[i]=max(d[i-1],d[i]);
    }
    long long maxim=d[1];
    for(i=2;i<=n;++i)
        if(d[i]>maxim)
            maxim=d[i];
    printf("%lld",maxim);
}