#include <stdio.h>
#include <stdlib.h>
void Queen(int n, int *count);
void printQueen(int q[], int n);
int place(int i, int j, int q[]);
int main() {
int n;
scanf("%d", &n);
int count = 0;
Queen(n, &count);
printf("%d\n", count);
return 0;
}
void Queen(int n, int *count) {
int i = 0;
int *q = (int *)malloc(n * sizeof(int));
q[0] = -1;
while (i >= 0) {
q[i]++;
while (!place(i, q[i], q) && q[i] < n) {
q[i]++;
}
if (q[i] < n) {
if (i == n - 1) {
(*count)++;
} else {
i++;
q[i] = -1;
}
} else {
i--;
}
}
free(q); // 释放动态分配的内存
}
void printQueen(int q[], int n) {
for (int i = 0; i < n; i++) {
printf("%d ", q[i] + 1);
}
printf("\n");
}
int place(int i, int j, int q[]) {
for (int k = 0; k < i; k++) {
if (q[k] == j || abs(q[k] - j) == abs(k - i))
return 0;
}
return 1;
}