nb，我开始还以为要用分数形式算，还用上gcd都溢出了

//P1035 [NOIP 2002 普及组] 级数求和
#include <bits/stdc++.h>
using namespace std;
int main(){
    int k;
    cin >> k;
    long long int kn = k;
    long long int a = 1, b = 1;
    long long int i = 1;
    while (a <= kn){
        i++;
        a = a * i + 1 * b;
        b = b * i;
        kn *= i;

        long long int r = __gcd(a, b);
        r = __gcd(r, kn);
        a /= r;
        b /= r;
        kn /= r;
        cout << a << "/" << b << " " << kn <<" "<<r<< "\n";
    }
    cout << i << endl;
}