#include<algorithm>
#include<bitset>
#include<cassert>
#include<cfloat>
#include<climits>
#include<cmath>
#include<deque>
#include<functional>
#include<iomanip>
#include<iostream>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<string>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<vector>

using namespace std;

using lint = long long;
using P = pair<int, int>;
using LLP = pair<long long, long long>;

#define REP(i, x, n) for(int i = (x), i##_len = (int)(n) ; i < i##_len ; ++i)
#define rep(i, n) for(int i = 0, i##_len = (int)(n) ; i < i##_len ; ++i)
#define reps(i, n) for(int i = 1, i##_len = (int)(n) ; i <= i##_len ; ++i)
#define rrep(i, n) for(int i = (int)(n) - 1 ; i >= 0 ; --i)
#define rreps(i, n) for(int i = (int)(n) ; i > 0 ; --i)
#define SORT(x) sort((x).begin(), (x).end())
#define SORT_INV(x) sort((x).rbegin(), (x).rend())
#define REVERSE(x) reverse((x).begin(), (x).end())
#define TWINS(x) cout << ((x) ? "Yay!" : ":(") << '\n'
#define endl '\n'

constexpr int IINF = (1 << 30) - 1;
constexpr long long LLINF = 1LL << 61;
constexpr double EPS = 1e-10;

constexpr int dx4[] = {1, 0, -1, 0}, dy4[] = {0, 1, 0, -1};
constexpr int dx8[] = {1, 1, 0, -1, -1, -1, 0, 1}, dy8[] = {0, -1, -1, -1, 0, 1, 1, 1};

template<typename T>
bool chmax(T& a, T b){
    if(a < b){
        a = b;
        return true;
    }
    return false;
}

template<typename T>
bool chmin(T& a, T b){
    if(b < a){
        a = b;
        return true;
    }
    return false;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    int m;
    cin >> m;

    vector<lint> d(m), c(m);
    rep(i, m){
        cin >> d[i] >> c[i];
    }

    LLP v[60][10];
    LLP t[19];
    rep(j, 19){
        if(j < 10){
            t[j] = make_pair(0LL, j);
        }else{
            t[j] = make_pair(1LL, j / 10 + j % 10);
        }
    }

    rep(j, 10){
        v[0][j] = make_pair(0LL, j);
    }
    REP(i, 1, 60){
        REP(j, 1, 10){
            LLP tmp = v[i - 1][j];
            LLP tmp2 = t[tmp.second + tmp.second];
            v[i][j] = make_pair(tmp.first * 2LL + tmp2.first + 1, tmp2.second);
        }
    }

    lint ans = 0;
    vector<lint> ls;
    rep(i, m){
        if(d[i] == 0LL){
            ans += c[i];
            continue;
        }
        lint now = c[i];
        vector<lint> hoge;
        rep(j, 60){
            if((now >> j) & 1LL){
                ans += v[j][d[i]].first;
                hoge.emplace_back(v[j][d[i]].second);
            }
        }
        while((int)hoge.size() > 1){
            ++ans;
            lint fuga = hoge.back();
            hoge.pop_back();
            fuga += hoge.back();
            hoge.pop_back();
            if(fuga < 10){
                hoge.push_back(fuga);
            }else{
                hoge.push_back(fuga / 10);
                hoge.push_back(fuga % 10);
            }
        }
        ls.push_back(hoge.back());
    }

    while((int)ls.size() > 1){
        ++ans;
        lint hoge = ls.back();
        ls.pop_back();
        hoge += ls.back();
        ls.pop_back();
        if(hoge < 10){
            ls.push_back(hoge);
        }else{
            ls.push_back(hoge / 10);
            ls.push_back(hoge % 10);
        }
    }

    cout << ans << endl;

    cout << flush;

    return 0;
}

Measured memory_bytes: 5620