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Cod sursa(job #638227)
#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstring>
using namespace std;
#define maxn 100
#define mod 9999991
#define LL long long
int N, sol = 1;
int V[maxn];
void back(int niv, int ram) {
if(niv == N + 1) {
int i, s = 0, ok = 1;
for(i=1; i<=N; i++) {
s += V[i];
if(s > i) {
ok = 0;
break;
}
}
if(ok && s == N) {
sol ++;
}
}
else {
int i;
for(i=0; i<=ram; i++) {
V[niv] = i;
back(niv+1, ram-i);
}
}
}
int x, y, aux;
void gcd(int a, int b) {
if(!b) x = 1, y = 0;
else {
gcd(b, a % b);
aux = x;
x = y;
y = aux - y * (a / b);
}
}
int main() {
FILE *f1=fopen("dirichlet.in", "r"), *f2=fopen("dirichlet.out", "w");
int i, j, p, q;
fscanf(f1, "%d\n", &N);
/**
for(i=N+2; i<=2*N; i++) {
sol = ((LL)sol * i) % mod;
}
for(i=2; i<=N; i++) {
LL inv = 0, ins;
gcd(inv, ins, i, mod);
if(inv <= 0) {
inv = mod + inv % mod;
}
sol = ((LL)sol * inv) % mod;
}
**/
sol = 1;
for(i=1; i<=N; i++) {
int aux = sol;
sol = ((LL)2 * (2*i-1) * aux) % mod;
//int inv = 0, ins;
//gcd(inv, ins, i+1, mod);
x = y = 0;
gcd(i+1, mod);
if(x <= 0) {
x = mod + x % mod;
}
sol = ((LL)sol * x) % mod;
}
fprintf(f2, "%d\n", sol);
fclose(f1); fclose(f2);
return 0;
}