#include <fstream>

using namespace std;
FILE * f;
long long p,i,cop=1,s=1;
int main()
{
    f=fopen("factorial.in","r");
    ofstream fout("factorial.out");
    fscanf(f,"%d",&p);
    while(p){
            p--;
            cop=cop*10;
    }
    p=cop;
    while(s){
   i=i+5;
   s=(s*i)%p;
    }
    fout<<i;
    fclose(f);
    fout.close();
    return 0;
}