CF 345A Mike and Frog

 1 #include <cstdio>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <cstdlib>
 5 
 6 #define LL long long
 7 
 8 using namespace std;
 9 
10 LL m,ans;
11 
12 LL gcd(LL a,LL b){
13     if(!b) return a;
14     return gcd(b,a%b);
15 }
16 
17 /*
18 since the f(x) be an fuction from a num x to y.
19 so it may be a cricle.
20 */
21 
22 void solve(LL &ansv,LL &sumv){
23     LL h,a,x,y,ans=0;
24     scanf("%I64d%I64d%I64d%I64d",&h,&a,&x,&y);
25     for(int i=1;i<=m;i++){
26         h=(h*x%m+y)%m;
27         if(h==a){
28             ansv=(LL)i;    //how many seconds it would take for us to arrive ‘a‘ from ‘h‘
29             goto L;
30         }
31     }
32     puts("-1");
33     exit(0);
34     L:h=a;
35     sumv=-1;
36     for(int i=1;i<=m;i++){
37         h=(h*x%m+y)%m;    //how many seconds it would take for us to arrive ‘a‘ from ‘a‘
38         if(h==a){
39             sumv=(LL)i;
40             return;
41         }
42     }
43 }
44 
45 /*
46 a1 + k1*a2 = b1 + k2*b2
47 
48 ans = a1 (mod a2)
49 ans = b1 (mod b2)
50 */
51 
52 int main(){
53     scanf("%I64d",&m);
54     LL a1,a2,b1,b2;
55     solve(a1,a2);
56     solve(b1,b2);
57     if(a1==b1) ans=a1;
58     else if(a2==-1&&b2==-1){
59         puts("-1");
60         return 0;
61     }
62     else if(a2==-1&&a1>b1&&(a1-b1)%b2==0) ans=a1;
63     else if(b2==-1&&b1>a1&&(b1-a1)%a2==0) ans=b1;
64     else if(a2==-1||b2==-1){
65         puts("-1");
66         return 0;
67     }
68     else{
69         LL k1;
70         for(k1=0;k1<=m;k1++)
71             if((a1+k1*a2-b1)%b2==0){
72                 ans=a1+k1*a2;
73                 if(ans>=b1) break;
74             }
75         if(k1>m) ans=-1;
76     }
77     printf("%I64d\n",ans);
78     return 0;
79 }