#include <stdio.h>
#include <math.h>

int main(void) {
	int tests[] = { 1, 5, 10, 25, 100, 125, 250, 625, 1000 };
	int num_tests = sizeof(tests) / sizeof(tests[0]);
	int i;

	for (i = 0; i < num_tests; ++i)
	{
		int x = tests[i];
		int n = (int)(log(x) / log(5)); // get n = log5(x), truncated to integer
        if (pow(5, n) == x)         // test to see whether x == 5^n
            printf("%d is a power of 5\n", x);
        else
            printf("%d is not a power of 5\n", x);
	}
	return 0;
}