#include <bits/stdc++.h>
using namespace std;
int main(void) {
  cin.tie(0);
  ios_base::sync_with_stdio(false);
  int a, ta, b, tb;
  string t;
  cin >> a >> ta >> b >> tb >> t;
  int p =
      600 * (t[0] - '0') + 60 * (t[1] - '0') + 10 * (t[3] - '0') + t[4] - '0';
  int q = p + ta;
  int ans = 0, i;
  for (i = 300; i < 1440; i += b) {
    if (p * (ta + tb) < ta * tb + p * tb + i * ta &&
        ta * tb + p * tb + i * ta < q * (ta + tb))
      ans++;
  }
  cout << ans << endl;
  return 0;
}
