#include <stdio.h>
#include <stdlib.h>


int calc(int n);

int main()
{
    FILE* in = fopen("fact.in","r");
    FILE* out = fopen("fact.in","r");
    int n;
    fscanf(in,"%d",&n);

    int c = calc(n);
    printf("%d",c);
    return 0;
}

int calc(int n)
{
    long long factSoFar = 1;
    int nrOfZeros = 0;
    int counter = 2;
    while(nrOfZeros != n)
    {
        int cNext = counter+1;
        if(cNext%10==0)
        {
            nrOfZeros++;
        }
        else if((cNext%5==0 && factSoFar%2==0 && !(factSoFar%10==0)) || (cNext%2==0 && factSoFar%5==0 && !(factSoFar%10==0)))
        {
            nrOfZeros++;
        }
        factSoFar *= counter;
        counter++;
    }
    //printf("%d",factSoFar);
    return counter;
}