SWUST OJ 青蛙的约会之二(0481)

 1 #include<iostream>
 2 using namespace std;
 3  
 4 long long int exgcd(long long int a,long long int b,long long int &x,long long int &y)
 5 {
 6     if(b==0)
 7     {
 8         x=1;
 9         y=0;
10         return a;
11     }
12     long long int gcd=exgcd(b,a%b,x,y);
13     long long int x2=x,y2=y;
14     x=y2;
15     y=x2-(a/b)*y2;
16     return gcd;
17 }
18  
19 int main()
20 {
21     long long int x,y,n,m,l,a,b,c,gcd,t;
22     while(cin>>x>>y>>m>>n>>l)
23     {
24         a=n-m;
25         b=l;
26         c=x-y;
27         gcd=exgcd(a,b,x,y);
28         if(c%gcd!=0)
29             cout<<"Impossible"<<endl;
30         else
31         {
32             c/=gcd;
33             x*=c;
34             x=(x%b+b)%b;
35             cout<<x<<endl;
36         }
37     }
38     return 0;
39 }