one-file-projects/euler1.c

#include <stdio.h>

int numbersum(int i, int p) {
    int n = p/i;
    return i*n*(n+1)/2;
}

int main( int argc, char *argv[] ) {
	int n = 999;
    int s = numbersum(3,n) + numbersum(5,n) - numbersum(15,n);
    printf("%d\n",s);
	return 0;
}