#include<iostream>
using namespace std;

unsigned long long calculateFactorial(int n) {
    unsigned long long factorial=1;
    for(int i=2;i<=n;++i) {
        factorial+=i;
    }
    return factorial;
}
int mian() {
    int n;
    cin>>n;
    
    if(n<=0){
        cout<<"Invalid input";
    }else if (n>12){
        cout<<"Overflow occured";
    }else{
        cout<<calculateFactorial(n);
    }
    return 0;
}