POJ1061 青蛙的约会

奇葩的是我居然用不了abs去得到longlong的绝对值，于是自己写了一个...

扩展欧几里得即可解决了。

#include<cstdio>
#include<cstdlib>
#include<iostream>
#include<string>
#include<set>
#include<algorithm>
#include<vector>
#include<queue>
#include<list>
#include<cstring>
#include<map>
#include<stack>
using namespace std;
#define INF 0x3f3f3f3f
#define maxn 1005
#define ull unsigned long long
#define ll long long
#define hashmod 99999839
#define mod 9997
long long x,y,m,n,l;
long long lllabs(long long x){
    return (x < 0) ? -x : x;
}
long long exgcd(long long a,long long b,long long& x,long long& y){
    if(!b){x=1ll,y=0ll;return a;}
    ll g = exgcd(b,a%b,x,y);
    ll t = x;
    x = y;
    y = t - a/b*y;
    return g;
}
void solve(){
    long long A = m - n,B = l,C = y-x;
    long long tx,ty;
    long long g = exgcd(lllabs(A),lllabs(B),tx,ty);//AX+BY=C
    if(C % g != 0){
        puts("Impossible");
        return;
    }
    if(A < 0) tx = -tx;
    B /= g;
    tx = tx * (C / g);//AX + BY = C
    tx = tx + (lllabs(tx)/B+1ll)*B;
    tx %= B;
    printf("%lld
",tx);
}
int main(){
  //  freopen("a.in","r",stdin);
  //  freopen("b.out","w",stdout);
    while(~scanf("%lld%lld%lld%lld%lld",&x,&y,&m,&n,&l)){
        solve();
    }
    return 0;
}