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  1. #include <cstdio>
  2. #include <cstring>
  3. #include <algorithm>
  4. using namespace std;
  5.  
  6. typedef long long LL;
  7. const int MOD = 1000000007;
  8.  
  9. void mul(int a[2][2], int b[2][2], int u[2][2]){
  10.     for(int i=0;i<2;i++) for(int j=0;j<2;j++){
  11.         LL tmp=0;
  12.         for(int k=0;k<2;k++) tmp+=LL(a[i][k])*b[k][j];
  13.         u[i][j]=tmp%MOD;
  14.     }
  15. }
  16.  
  17. void pow(int a[2][2], int n){
  18.     if(n==1) return;
  19.     int u[2][2],r[2][2];
  20.     memcpy(u,a,sizeof(u));
  21.     pow(u,n/2);
  22.     if(n%2){
  23.         mul(u,a,r);
  24.         mul(u,r,a);
  25.     }else{
  26.         mul(u,u,a);
  27.     }
  28. }
  29.  
  30. int main(){
  31.     int n,m,k;
  32.     while(scanf("%d%d%d",&n,&m,&k)==3){
  33.         int a[2][2]={
  34.             {k-1,k},
  35.             {m-k,m-k}
  36.         };
  37.         pow(a,n);
  38.         int ans=(a[0][1]+a[1][1])%MOD;
  39.         printf("%d\n",ans);
  40.     }
  41. }
  42.  
Not running #stdin #stdout 0s 0KB
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https://ideone.com/LPSNL2
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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