#include <stdio.h>
int zero(int n){
    int r;
    r=0;
    while(n>=5){
        r+=n/5;
        n/=5; }
    return r; }
int caut(int p){
    long long i,pas=1<<30;
    i=0;
    while(pas!=0){
        if(zero(i+pas)<p)
          i+=pas;
        pas/=2; }
    return i+1; }
int main(){
    int p;
    freopen("fact.in","r",stdin);
    freopen("fact.out","w",stdout);
    scanf("%d",&p);
    printf("%d",caut(p));
}