#pragma GCC optimize ("O3")
#pragma GCC target ("avx")
#include "bits/stdc++.h"

using namespace std;
using ll = long long int;

#define debug(v) {printf("L%d %s > ",__LINE__,#v);cout<<(v)<<endl;}
#define debugv(v) {printf("L%d %s > ",__LINE__,#v);for(auto e:(v)){cout<<e<<" ";}cout<<endl;}
#define debuga(m,w) {printf("L%d %s > ",__LINE__,#m);for(int x=0;x<(w);x++){cout<<(m)[x]<<" ";}cout<<endl;}
#define debugaa(m,h,w) {printf("L%d %s >\n",__LINE__,#m);for(int y=0;y<(h);y++){for(int x=0;x<(w);x++){cout<<(m)[y][x]<<" ";}cout<<endl;}}
#define ALL(v) (v).begin(),(v).end()
#define repeat(cnt,l) for(remove_const<decltype(l)>::type cnt=0;(cnt)<(l);++(cnt))
#define rrepeat(cnt,l) for(auto cnt=(l)-1;0<=(cnt);--(cnt))
#define iterate(cnt,b,e) for(auto cnt=(b);(cnt)!=(e);++(cnt))
#define diterate(cnt,b,e) for(auto cnt=(b);(cnt)!=(e);--(cnt))
// const ll MD = 1000000007ll; const long double PI = 3.1415926535897932384626433832795L;
template<typename T1, typename T2> inline void assert_equal(T1 expected, T2 actual) { if (!(expected == actual)) { cerr << "assertion fault: expected=" << expected << " actual=" << actual << endl; abort(); } }
template<typename T1, typename T2> inline void assert_less(T1 actual, T2 threshold) { if (!(actual < threshold)) { cerr << "assertion fault: " << actual << " < (const)" << threshold << endl; abort(); } }
template<typename T1, typename T2> inline void assert_eqless(T1 actual, T2 threshold) { if (!(actual <= threshold)) { cerr << "assertion fault: " << actual << " <= (const)" << threshold << endl; abort(); } }
template<typename T1, typename T2> inline ostream& operator <<(ostream &o, const pair<T1, T2> p) { o << '(' << p.first << ':' << p.second << ')'; return o; }
template<typename Vec> inline ostream& _ostream_vecprint(ostream &o, const Vec& p) { o << '['; for (auto& e : p) o << e << ','; o << ']'; return o; }
template<typename T> inline ostream& operator<<(ostream& o, const vector<T>& v) { return _ostream_vecprint(o, v); }
template<typename T, size_t S> inline ostream& operator<<(ostream& o, const array<T, S>& v) { return _ostream_vecprint(o, v); }
template<typename T> inline T& maxset(T& to, const T& val) { return to = max(to, val); }
template<typename T> inline T& minset(T& to, const T& val) { return to = min(to, val); }
void bye(string s, int code = 0) { cout << s << endl; exit(code); }
mt19937_64 randdev(8901016);
template<typename T> inline T rand(T l, T h) { return uniform_int_distribution<T>(l, h)(randdev); }
template<> inline double rand<double>(double l, double h) { return uniform_real_distribution<double>(l, h)(randdev); }
template<> inline float rand<float>(float l, float h) { return uniform_real_distribution<float>(l, h)(randdev); }

#if defined(_WIN32) || defined(_WIN64)
#define getchar_unlocked _getchar_nolock
#define putchar_unlocked _putchar_nolock
#elif defined(__GNUC__)
#else
#define getchar_unlocked getchar
#define putchar_unlocked putchar
#endif
namespace {
#define isvisiblechar(c) (0x21<=(c)&&(c)<=0x7E)
    class MaiScanner {
    public:
        template<typename T> void input_integer(T& var) {
            var = 0; T sign = 1;
            int cc = getchar_unlocked();
            for (; cc<'0' || '9'<cc; cc = getchar_unlocked())
                if (cc == '-') sign = -1;
            for (; '0' <= cc && cc <= '9'; cc = getchar_unlocked())
                var = (var << 3) + (var << 1) + cc - '0';
            var = var * sign;
        }
        inline int c() { return getchar_unlocked(); }
        inline MaiScanner& operator>>(int& var) { input_integer<int>(var); return *this; }
        inline MaiScanner& operator>>(long long& var) { input_integer<long long>(var); return *this; }
        inline MaiScanner& operator>>(string& var) {
            int cc = getchar_unlocked();
            for (; !isvisiblechar(cc); cc = getchar_unlocked());
            for (; isvisiblechar(cc); cc = getchar_unlocked())
                var.push_back(cc);
            return *this;
        }
        template<typename IT> void in(IT begin, IT end) { for (auto it = begin; it != end; ++it) *this >> *it; }
    };
    class MaiPrinter {
    public:
        template<typename T>
        void output_integer(T var) {
            if (var == 0) { putchar_unlocked('0'); return; }
            if (var < 0)
                putchar_unlocked('-'),
                var = -var;
            char stack[32]; int stack_p = 0;
            while (var)
                stack[stack_p++] = '0' + (var % 10),
                var /= 10;
            while (stack_p)
                putchar_unlocked(stack[--stack_p]);
        }
        inline MaiPrinter& operator<<(char c) { putchar_unlocked(c); return *this; }
        inline MaiPrinter& operator<<(int var) { output_integer<int>(var); return *this; }
        inline MaiPrinter& operator<<(long long var) { output_integer<long long>(var); return *this; }
        inline MaiPrinter& operator<<(char* str_p) { while (*str_p) putchar_unlocked(*(str_p++)); return *this; }
        inline MaiPrinter& operator<<(const string& str) {
            const char* p = str.c_str();
            const char* l = p + str.size();
            while (p < l) putchar_unlocked(*p++);
            return *this;
        }
        template<typename IT> void join(IT begin, IT end, char sep = '\n') { for (auto it = begin; it != end; ++it) *this << *it << sep; }
    };
}
MaiScanner scanner;
MaiPrinter printer;


const ll MOD = 998244353;


ll N, M, K;

/*
string str;

ll dp[200010][3];

void problemD() {

scanner >> str;
N = str.size();
}

*/

const int Tozan = 0, Gezan = 1;

int guchokuGezan(vector<ll>&, vector<ll>&);

int guchokuTozan(vector<ll>& aa, vector<ll>& bb) {
    if (aa == bb) return 0;

    int best = 0;
    repeat(i, N) {
        if (aa[i] == 0) continue;
        aa[i] -= 1;
        maxset(best, guchokuGezan(aa, bb));
        aa[i] += 1;
    }
    return best;
}

int guchokuGezan(vector<ll>& aa, vector<ll>& bb) {

    int best = 1e9;
    repeat(i, N) {
        if (bb[i] == 0) continue;
        bb[i] -= 1;
        minset(best, guchokuTozan(aa, bb) + 1);
        bb[i] += 1;
    }
    return best;

}

/*
tozan君の最大化：
aa[i] > bb[i] なる要素があるならば，それを最後までとっておく
必ず存在する．
複数あるならば，aa[i]>bb[i]の中でbb[i]が最小の要素を取っておく．

gezan君の最小化：
aa[i] < bb[i] なる要素があるならば，それを選ぶ
必ず存在する
*/

// int guchokuTozanGezan(vector<ll>& aa, vector<ll>& bb) {
//     if (aa == bb) return 0;
// 
//     int best = 1e9, idxa, idxb;
//     repeat(i, N) {
//         if (aa[i] > bb[i]) {
//             if (aa[i] < best)
//                 best = aa[i],
//                 idxa = i;
//         }
//         if (aa[i] < bb[i]) {
// 
//         }
//     }
//     return best;
// }

ll solveTozanGezan(vector<ll>& aa, vector<ll>& bb) {
    if (aa == bb) return 0;

    ll sum = accumulate(ALL(aa), 0ll);

    ll best = 1e18, idxa, idxb;
    repeat(i, N) {
        if (aa[i] > bb[i]) {
            if (bb[i] < best)
                best = bb[i],
                idxa = i;
        }
    }

    return sum - bb[idxa];
}


void test() {
    vector<ll> aa, bb;
    N = 3;
    aa.resize(N), bb.resize(N);
    repeat(_, 1000) {
        if (_%10 == 0) cout << _ << endl;
        ll asum = 0, bsum = 0;
        repeat(i, N) {
            asum += aa[i] = rand(0, 4);
            bsum += bb[i] = rand(0, 4);
        }
        if (asum > bsum)
            bb[N-1] += asum - bsum;
        else
            aa[N-1] += bsum - asum;
        
        auto bestg = guchokuTozan(aa, bb);
        auto best = solveTozanGezan(aa, bb);
        
        if (bestg != best){
            debugv(aa);
            debugv(bb);
            assert_equal(bestg, best);
        }
    }
    
}


int main() {
    //test();
    vector<ll> aa, bb;

    scanner >> N;

    aa.reserve(N);
    bb.reserve(N);
    repeat(i, N) {
        ll a, b;
        scanner >> a >> b;
        aa.push_back(a);
        bb.push_back(b);
    }

    //auto bestg = guchokuTozan(aa, bb);

    auto best = solveTozanGezan(aa, bb);

    //cout << make_pair(bestg, best) << endl;

    cout << best << endl;




    return 0;
}

Measured memory_bytes: 512