#include<stdio.h>
int main()
{
    unsigned long long hour1,minute1,second1,time1,hour2,minute2,second2,time2,c,number;
    scanf("%d:%d:%d\n%d:%d:%d\n%d",&hour1,&minute1,&second1,&hour2,&minute2,&second2,&c);
    time1=hour1*3600+minute1*60+second1;
    time2=hour2*3600+minute2*60+second2;
    number=c*(time2-time1);
    printf("%lld\n",number);
    return 0;
}