#include<bits/stdc++.h>

using namespace std;

#define MAXN 50010

typedef long long LL;

const LL inf = 1e18;

struct info

{

        LL x , y;

} a[MAXN];

int n;

template <typename T> inline void chkmax(T &x,T y) { x = max(x,y); }

template <typename T> inline void chkmin(T &x,T y) { x = min(x,y); }

template <typename T> inline void read(T &x)

{

    T f = ; x = ;

    char c = getchar();

    for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;

    for (; isdigit(c); c = getchar()) x = (x << ) + (x << ) + c - '';

    x *= f;

}

inline bool cmp(info a , info b)

{

        return a.x + a.y < b.x + b.y;

}

int main()

{

        read(n);

        for (int i = ; i <= n; i++)

        {

                read(a[i].x);

                read(a[i].y);

        }

        sort(a +  , a + n +  , cmp);

        LL ans = -inf , now = ;

        for (int i = ; i <= n; i++)

        {

                chkmax(ans , now - a[i].y);

                now += a[i].x;

        }

        cout<< ans << '\n';

        return ;

}