青蛙的约会(裸扩展欧几里德)

 1 #include<iostream>
 2 #include<algorithm>
 3 #include<cstdio>
 4 #include<cstring>
 5 #include<cmath>
 6 #include<vector>
 7 #define mem(x,y) memset(x,y,sizeof(x))
 8 using namespace std;
 9 const int INF=0x3f3f3f3f;
10 typedef long long LL;
11 void e_gcd(LL a,LL b,LL &d,LL &x,LL &y){
12     if(!b){
13         d=a;
14         x=1;
15         y=0;
16     }
17     else{
18         e_gcd(b,a%b,d,x,y);
19         LL temp=x;
20         x=y;
21         y=temp-a/b*y;
22     }
23 }
24 LL cal(LL a,LL b,LL c){
25     LL d,x,y;
26     e_gcd(a,b,d,x,y);
27     if(c%d!=0)return -1;
28     x*=c/d;
29     if(b<0)b=-b;
30     b/=d;
31     LL ans=x%b;
32     if(ans<=0)ans+=b;
33     return ans;
34 }
35 int main(){
36     LL x,y,m,n,L;
37     while(~scanf("%lld%lld%lld%lld%lld",&x,&y,&m,&n,&L)){
38         LL ans=cal(n-m,L,x-y);
39         if(ans==-1)puts("Impossible");
40         else printf("%lld\n",ans);
41     }
42     return 0;
43 }