From https://www.google.at/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=c%20find%20number%20wich%20is%20divadable%20by%20all%2020

new_gist_file_0

#include <stdio.h>

#define MY_TRUE 0
#define MY_FALSE -1
#define MAX_NUM 20

int num_is_dividable(int num);

int main(int argc, char ** argv) {

	int current=1;
	int result=MY_FALSE;
	while(num_is_dividable(current) == MY_FALSE) {
			current++;
	}
	printf("DONE: %d\n", current);
}
int num_is_dividable(int num) {
	int x;
	int is_dividable=MY_TRUE;

	for(x = 1; x<=MAX_NUM; x++) {
		if(num%x != 0) {
			is_dividable=MY_FALSE;
		}
	}
	if(is_dividable == MY_FALSE) {
		return MY_FALSE;
	} else {
		return num;
	}
	return MY_FALSE;
}