#include <bits/stdc++.h>
using namespace std;
const long long MOD = 1e9 + 7;
long long add(long long x, long long y, long long CMOD = MOD) {
  return (x + y + CMOD + CMOD) % CMOD;
}
long long mult(long long x, long long y, long long CMOD = MOD) {
  return add(x, 0) * add(y, 0) % CMOD;
}
long long fast_expo(long long x, long long y, long long CMOD = MOD) {
  if (x == 0) return 0;
  if (y == 0) return 1;
  long long ans = fast_expo(x, y / 2, CMOD);
  ans = mult(ans, ans, CMOD);
  if (y & 1) ans = mult(ans, x, CMOD);
  return ans;
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
long long gen(long long x, long long y) {
  if (x == y) return x;
  return x + rng() % (y - x + 1);
}
const int TAM = 1e5 + 100;
const long long INF = LLONG_MAX / 4;
int n;
int a[TAM];
int b[TAM];
string s;
int main() {
  ios_base ::sync_with_stdio(false);
  cin.tie(NULL);
  cin >> n >> s;
  for (int i = 0; i < n; i++) cin >> a[i] >> b[i];
  int ans = 0;
  for (int t = 0; t <= TAM; t++) {
    int cont = 0;
    for (int i = 0; i < n; i++) {
      if (t < b[i])
        cont += s[i] - '0';
      else {
        int t2 = t - b[i];
        int p = t2 / a[i];
        if (p % 2 == 0)
          cont += s[i] == '0' ? 1 : 0;
        else
          cont += s[i] - '0';
      }
    }
    ans = max(ans, cont);
  }
  cout << ans << endl;
  return 0;
}
