#include <stdio.h>
#include <string.h>

int FindZeros(int someNumber){

int zeros=0, i;

while(someNumber>0){
    i = someNumber;
        while(i){
            if(!(i%5)){
                zeros++;
                i /= 5;
            }else i=0;
        }
    someNumber--;
}
return zeros;
}

int main(){

FILE *file1, *file2;
int P, i;

file1 = fopen("fact.in", "r");
file2 = fopen("fact.out", "w");

fscanf(file1, "%d", &P);

for(i=1;;i++){
    if(FindZeros(i)==P){
        fprintf(file2, "i: %d", i);
        break;
    }
    if(FindZeros(i)>P){
        fprintf(file2, "%d", -1);
        break;
    }
}
return 0;
}