Add C solution

Author: randomite

1/Main.c

@@ -0,0 +1,11 @@
+#include <stdio.h>
+
+int main(int argc, char *argv[]) {
+	int x=0;
+	for (int i=1;i<1000;i++) {
+		if (i%3 == 0 || i%5 == 0) {
+			x+=i;
+		}	
+	}
+	printf("%d",x);
+}