#include <iostream> using namespace std; int main() { //阶乘：n的阶乘=1*2*3*4*...*n //0的阶乘=1 //n! int m; cin>>m; if (m < 1) { cout<<0; return 0; } if (m == 1) { cout<<2; return 0; } int i = 1; int mul = 1; while (true) { mul *= i; if (mul > m) { cout<< i; return 0; } i++; } }