没问题，是用递归的，只不过

#include<cstdio>
int 
f
(
int 
x
)
{
    if
        (
        x
        <=
        1
        )
        return 
            1
            ;
    return 
        x*
        f
        (
        x
        -
        1
        )
        ;
}int
main
(

)
{
    int 
    x
    ;
    scanf
        (
        "%d"
        ,
        &
        x
        )
        ;
    printf
        (
        "%d",
        f
        (
        x
        )
        )
        ;
    return
        0
        ;
}