#include <stdio.h>

int main() {
    char *inFileName = "fact.in";
    char *outFileName = "fact.out";
    FILE *in = fopen(inFileName, "r");
    if (in == NULL) {
        printf("Cannot open %s.\n", inFileName);
        return 1;
    }
    FILE *out = fopen(outFileName, "w");
    int p;
    fscanf(in, "%d", &p);
    int count = 0;
    int current;
    for (current = 1; count < p; ++current) {
        int clone = current;
        while (clone % 10 == 0) {
            clone /= 10;
            count++;
        }
        while (clone % 5 == 0) {
            clone /= 5;
            count++;
        }
    }
    if (count == p) {
        fprintf(out, "%d", current - 1);
    } else {
        fprintf(out, "%d", -1);
    }

    fclose(in);
    fclose(out);
    return 0;
}