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  1. #include<stdio.h>
  2. using lld = long long int;
  3. // solution from https://h...content-available-to-author-only...n.hr/studenti2020/
  4. // See https://e...content-available-to-author-only...a.org/wiki/Fuss%E2%80%93Catalan_number
  5.  
  6. constexpr lld M = 1'000'000'007;
  7. int n,m;
  8. lld expp(lld p,lld q){
  9.     lld r=1;
  10.     lld z=p;
  11.     while(q){
  12.         if(q&1)r=r*z%M;
  13.         z=z*z%M;
  14.         q>>=1;
  15.     }
  16.     return r;
  17. }
  18. int main(){
  19.     scanf("%d%d",&n,&m);
  20.     // nm C n / (nm-n+1)
  21.     lld p=(lld)n*m;
  22.     lld r=1;
  23.     lld f=n;
  24.     for(int i=1;i<n;i++){
  25.         r=r*(p--)%M;
  26.         f=f*i%M;
  27.     }
  28.     r=r*expp(f,M-2)%M;
  29.     printf("%lld",r);
  30. }
Success #stdin #stdout 0.01s 5308KB
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https://ideone.com/D1DFi6
language:
C++14 (gcc 8.3)
created:
1 day ago
visibility:
public

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