#include int main() { unsigned upper_bound = 1000000, sum = 0, iteration = 0; for(int i = 3; i < upper_bound; i += 3) sum += i; for(int i = 5; i < upper_bound; i += 15) sum += i; for(int i = 10; i < upper_bound; i+= 15) sum += i; printf("%i\n", sum); }