I cant understand this problem... what are this "pairs of ties " and "long serial numbers of ties"

small a,
big b,
big n,
and the LCM of a and b is larger than n.
such as
3 24999998 25000000


Edited by author 21.03.2010 23:41

i divide n numbers into ceil[n/a] segments
for each segment, increasing B's ties by add b until it reach a, and count the pairs.

such like this:
while(j + b <= a) {
    ans += j * b;
    j += b;
}