#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using Pi = pair<int, int>;
using Pl = pair<ll, ll>;
using vint = vector<int>;
using vvint = vector<vint>;
using vvvint = vector<vvint>;
using vll = vector<ll>;
using uint = unsigned int;
using ull = unsigned long long;
template<typename T> using uset = unordered_set<T>;
template<typename T1, typename T2> using umap = unordered_map<T1, T2>;
constexpr int INF = (1 << 30) - 1;
constexpr ll LLINF = 1LL << 60;
constexpr int dy[] = {1, 0, -1, 0, 1, -1, -1, 1};
constexpr int dx[] = {0, 1, 0, -1, 1, 1, -1, -1};
constexpr char el = '\n';
constexpr int mod = 1000000007;
template<typename T> T gcd(T a, T b) { return (b ? gcd(b, a % b) : a); }
template<typename T> T lcm(T a, T b) { return (a / gcd(a, b) * b); }
template<typename T1, typename T2> inline void chmin(T1 &a, T2 b) { if (a > b) a = b; }
template<typename T1, typename T2> inline void chmax(T1 &a, T2 b) { if (a < b) a = b; }
template<typename T>
ostream& operator <<(ostream &os, vector<T> &v) {
for (auto &u : v) os << u << el;
return (os);
}
template<typename T>
istream& operator >>(istream &is, vector<T> &v) {
for (auto &u : v) is >> u;
return (is);
}
template<typename T1, typename T2>
istream& operator >>(istream &is, pair<T1, T2> &p) {
return (is >> p.first >> p.second);
}
int main() {
int N;
int cnt[200001] = {};
const int day = 86400;
const int span = 10801;
const int MAX = 200000;
cin >> N;
int sum = 0;
for (int i = 0; i < N; i++) {
int A, B;
cin >> A >> B;
(sum += A) %= day;
cnt[sum]++;
(sum += B) %= day;
}
for (int i = day; i <= MAX; i++) cnt[i] = cnt[i-day];
int num = 0;
for (int i = 0; i < span; i++) {
num += cnt[i];
}
int maxv = num;
for (int i = span; i <= MAX; i++) {
num -= cnt[i-span];
num += cnt[i];
chmax(maxv, num);
}
cout << maxv << endl;
return (0);
}