#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);
    if (p == 0) {
        fprintf(out, "%d", 1);
    } else {
        int count = 0;
        int current;
        int powers[12] = {0};
        for (current = 1; count < p; current++) {
            count++;
            powers[0]++;
            for (int i = 0; i < 11; ++i) {
                if (powers[i] % 5 == 0) {
                    powers[i + 1]++;
                    count++;
                } else {
                    break;
                }
            }
        }
        if (count == p) {
            fprintf(out, "%d", (current - 1) * 5);
        } else {
            fprintf(out, "%d", -1);
        }
    }
    fclose(in);
    fclose(out);
    return 0;
}