#include <stdio.h>
int factorial(int N){
int sum=1;
int i;
for (i=1;i<=N;i++){
sum*=i;
}
return sum;
}
int main(){
int N;
int sum=0;
int i;
int res;
int f;
res = scanf("%d",&N);
if (res!=EOF){
for (i=1;i<=N;i++){
f = factorial(i);
//printf("i=%d f=%d\n",i,f);
sum+=f;
}
}else{
printf("something wrong");
}
printf("%d",sum);
return 0;
}
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