int chtime()
{
int cnt = 0,a1 = 0,a2 = 0,b1 = 0,b2 = 0;
while (s1[cnt] != ':') {
a1 = a1 * 10 + s1[cnt++];
}
cnt++;
while (s1[cnt] != 0) {
b1 = b1 * 10 + s1[cnt++];
}
cnt = 0;
while (s2[cnt] != ':') {
a2 = a2 * 10 + s2[cnt++];
}
cnt++;
while (s2[cnt] != 0) {
b2 = b2 * 10 + s2[cnt++];
}
return (a2 - a1) * 60 + (b2 - b1);
}
