程序代码：

#include <stdio.h>

void multi(int *p, int k, int *n);

int dat[101], res[100];

int main()
{
    int i, j, n, cnt;
    
    printf("Input N: ");
    scanf("%d", &n);
    
    for (i = 1; i <= n; i++) dat[i] = i;
    
    for (res[0] = cnt = i = 1; i <= n; i++) {
        if (dat[i] == 1) continue;
        
        multi(res, dat[i], &cnt);
        for (j = 2; j * i <= n; j++) dat[j*i] /= dat[i];
    }
    
    printf("%d", res[cnt-1]);
    for (i = cnt-2; i >= 0; i--) 
        printf("%04d", res[i]);
    
    return 0;
}

void multi(int *p, int k, int *n)
{
    int i, c, tmp;
    
    for (c = i = 0; i < *n; i++) {
        tmp = p[i] * k;
        p[i] = c + tmp % 10000;
        c = tmp / 10000;
    }
    
    if (c > 0) p[(*n)++] = c;
}