#include<stdio.h>

int main(){
    int n;
    
    scanf("%d",&n);
    
    if(n<0){
        printf("Invalid input");
        return 0;
    }
    
    int factorial = 1;
     
    for(int i=1;i<=n;i++){
        factorial *=i;
    }
    
    printf(factorial);
}