#include <iostream>
#include <cmath>
using namespace std;

int GetLength(double x);

int main()
{
int n; cin>>n;
double y=1;
for(int x=2; x<=n; x++)
y=y*x;
cout<<GetLength(y)<<endl;
return 0;
}
int GetLength(double x)
{
int n=0;
while(x>=1) // !!!!
n++, x/=10;
return n;
}

int GetLength(int x)
{
int n; cin>>n;
double len=0;
for(int i=1; i<=n; i++)
len += log(i)/log(10);
cout << (int)len + 1;
return 0;
}

#include <iostream>
#include <cmath>
using namespace std;
int GetLength(double x);
int main()
{
int n; cin>>n;
double y=1;
for(int x=2; x<=n; x++)
y=y*x;
cout<<GetLength(y)<<endl;
return 0;
}
int GetLength(double x)
{
int n=0;
while(x>=1) // !!!!
n++, x/=10;
return n;
}
int GetLength(int x)
{
int n; cin>>n;
double len=0;
for(int i=1; i<=n; i++)
len += log(i)/log(10);
cout << (int)len + 1;
return 0;
}