#include <bits/stdc++.h>

using namespace std;

/**
 * 功能：将字符串转为整数
 * 作者：黄海
 * 时间：2019-11-24
 * @param str
 * @return
 */
unsigned int stou(const string &str) {
    unsigned int n;
    stringstream ssTmp(str);
    ssTmp >> n;

    return n;
}

long long getSenconds(string temp) {
    int count = 0;
    int shi, fen, miao = 0;

    string str = "";
    for (int i = 0; i < temp.size(); i++) {
        if (temp[i] != ':') {
            str += temp[i];
        } else {
            count++;
            if (count == 1) shi = stou(str);
            if (count == 2) fen = stou(str);
            str = "";
        }
    }
    miao = stou(str);
    return shi * 60 * 60 + fen * 60 + miao;
}


int main() {
    ios::sync_with_stdio(false); //读入输出优化的强迫症

    string a, b;
    int c;
    cin >> a >> b >> c;
    long long q = getSenconds(b) - getSenconds(a);
    cout << q * c << endl;
    return 0;
}