#include // returns sum of squares of digits of n unsigned int sum_square_digits(unsigned int n) { int i,num=n,sum=0; // process digits one at a time until there are none left while (num > 0) { // peal off the last digit from the number int digit=num % 10; num=(num - digit)/10; // add it's square to the sum sum+=digit*digit; } return sum; } int main(void) { unsigned int i=0,result=0, count=0; for (i=1; i<=100000000; i++) { // if not 1 or 89, start the iteration if ((i != 1) || (i != 89)) { result = sum_square_digits(i); } // otherwise we're done already else { result = i; } // while we haven't reached 1 or 89, keep iterating while ((result != 1) && (result != 89)) { result = sum_square_digits(result); } if (result == 89) { count++; } } std::cout << count << std::endl; return 0; }