luogu P1592 互质（欧拉函数）

 1 #include<iostream>
 2 #include<cstring>
 3 #include<cstdio>
 4 #include<cmath>
 5 #include<algorithm>
 6 using namespace std;
 7 int n,d,phi,c[1500000],tmp,ans,cnt;
 8 int gcd(int x,int y){
 9     if(x==0)return y;
10     if(y==0)return x;
11     return gcd(y,x%y);
12 }
13 void get_phi(){
14     for(int i=1;i<=n;i++){
15         if(gcd(i,n)==1){
16             phi++;
17             c[++cnt]=i;
18         }
19     }
20 }
21 int main(){
22     scanf("%d%d",&n,&d);
23     get_phi();
24     tmp=(d-1)/phi;
25     ans=(d-1)%phi+1;
26     printf("%d",c[ans]+tmp*n);
27     return 0;
28 }