a.cpp

#include <stdio.h>
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <functional>
#include <vector>
#include <string>
#include <queue>
#include <deque>
#include <cassert>
#include <set>
#include <map>

typedef long long ll;

int main() {
    // std::ios_base::sync_with_stdio(false);
    // std::cin.tie(0); std::cout.tie(0); std::cerr.tie(0);

    int d1, t1, d2, t2;
    scanf("%d %d %d %d", &d1, &t1, &d2, &t2);

    int h, m;
    scanf("%d:%d", &h, &m);
    m += h * 60;

    int s = 5 * 60, f = 23 * 60 + 59;

    int count = 0;
    for (int begin = s; begin <= f; begin += d2) {
        const int end = begin + t2;
        // (begin, end) с (m, m+t1)
        if (end <= m || begin >= m+t1) {
            continue;
        }
        ++count;
    }
    printf("%d", count);
    return 0;
}