#include <stdio.h>
#include <math.h>
int main(){
	int p, N = 1;
	FILE * f1;
	FILE * f2;
	f1 = fopen ("fact.in","r");
	f2 = fopen ("fact.out","w");
	fscanf (f1, "%d", &p);
	//scanf("%d",&p);
    while(p){
        N++;
        if(N % 5 == 0){
            int aux = N;
            while(aux % 5 == 0 && aux){
                aux /= 5;
                p--;
            }
        }
        //printf("N:%d\np:%d\n", N, p);
        //scanf("%d", &da);
    }
    //printf("N final:%d\n", N);
	fprintf(f2,"%d\n", N);
	fflush(stdout);
	fclose(f1);
	fclose(f2);
	return 0;
}