long recursin(int);void main(){    int n;    long result;    printf("input a integer number: \n");    scanf("%d", &n);    result = recursin(n);    printf("%d! = %ld\n", n, result);}long recursin(int n){    long temp_result;    if(n<0)    {        printf("n<0, input error!\n");    }    else if(n == 0 || n == 1)    {        temp_result = 1;    }    else    {        temp_result = recursin(n-1) * n;    }    return temp_result;}