double fact(int n){
    double result = 1;
    while(n > 0){
        result *= n--;
    }
    return result;
}
void main(){
    int limit = 1000;
    int n = 1;
    double e = 0;
    while(n < limit){
        e += 1 / fact(n++);
    }
    std::cout << e;
}