#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 k,n=1,sum=1; int main(){ cin>>k; while(1){ sum=sum*n; n+=1; if(sum>k){break;} } cout<<n-1; return 0; }