projecteuler.net/006/main.rs

fn main() {
    {   
        // SOLUTION 1
        let mut sum_1 = 0;
        let mut sum_a = 0;
        for i in 0..=100 {
            sum_1 += i;
            sum_a += i * i;
        }
        let diff = sum_1 * sum_1 - sum_a;
        println!("sum_1: {}", sum_1 * sum_1);
        println!("sum_a: {}", sum_a);
        println!("solution1: {}", diff);
    }

    {
        // SOLUTION 2
        let n = 100;
        let solution_2 = ( (n * (n + 1) ) / 2) * ( (n * (n + 1) ) / 2 ) - ( (n * (n + 1) * (2 * n + 1)) / 6 );
        println!("solution2: {}", solution_2);
    }

}