#include<iostream> // cin\cout\endl #include<cstdio> //scanf()\printf() #include<cstring> // strcpy()\strcat()\strcmp()\strlen()\memset() #include<cmath> //sqrt()\pow()\abs()\ceil()\floor()\max()\min() using namespace std; int main(){ int k,n=1,s=1; cin>>k; while(s<=k){ s=s*n; n++; } cout<<n-1<<endl; return 0; }