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Cod sursa(job #989901)
#include<fstream>
using namespace std;
const int mod=9999991;
int n,i,j;
long long fact[2000005];
long long pow(long long n, int p) {
long long rez=1;
while (p>0)
if (p%2==0) { n=(n*n)%mod; p/=2; }
else { rez=(rez*n)%mod; --p; }
return(rez%mod);
}
int c(int n, int k) {
int p1=fact[n],p2=(fact[k]*fact[n-k])%mod;
return((p1*pow(p2,mod-2))%mod);
}
int main(void) {
ifstream fin("dirichlet.in");
ofstream fout("dirichlet.out");
fin>>n;
fact[0]=1;
for (i=1; i<=2*n; ++i) fact[i]=(fact[i-1]*i)%mod;
int sol=c(2*n-1,n);
for (i=0; i<n-1; ++i) sol=(sol-c(n+i,n)+mod)%mod;
fout<<sol;
return(0);
}