poj-1061-exgcd

 1 #include<iostream>
 2 #include<cstdio>
 3 using namespace std;
 4 #define LL long long 
 5 #define mp make_pair
 6 #define pb push_back
 7 #define inf 0x3f3f3f3f
 8 void exgcd(LL a,LL b,LL &d,LL &x,LL &y){
 9     if(!b){d=a,x=1,y=0;}
10     else{
11         exgcd(b,a%b,d,y,x);
12         y-=x*(a/b);
13     }
14 }
15 int main(){
16     LL x,y,m,n,L;
17     while(cin>>x>>y>>m>>n>>L){
18         if(m<n){
19             swap(x,y);
20             swap(m,n);
21         }
22         LL a,b,d;
23         exgcd(m-n,L,d,a,b);
24         if((y-x)%d||m==n){
25             puts("Impossible");
26             continue;
27         }
28         printf("%lld\n",((a*(y-x)/d)%(L/d)+L/d)%(L/d));
29     }
30     return 0;
31 }