poj1061 青蛙的约会

1 #include <iostream>
2 #include <cstdio>
3
4 using namespace std;
5 typedef long long ll;
6
7 ll abs(ll x)
8 {
9     return x < 0 ? -x : x;
10 }
11
12 ll extgcd(ll a, ll b, ll & x, ll & y)
13 {
14     int d = a;
15     if (!b)
16     {
17         x = 1; y = 0;
18     }
19     else
20     {
21         d = extgcd(b, a % b, y, x);
22         y -= (a / b) * x;
23     }
24     return d;
25 }
26
27 int main()
28 {
29     ll x, y, m, n, L;
30     cin >> x >> y >> m >> n >> L;
31     ll ans, p, q;
32     ans = extgcd((m - n), L, p, q);
33     if ((y - x) % ans) puts("Impossible");
34     else
35     {
36         ll mod = abs(L / ans);
37         p = (p * (y - x) / ans % mod + mod) % mod;
38         cout << p << endl;
39     }
40     return 0;
41 }