#include <stdio.h>

int main(void) {
    int a, b, i, ans;

    printf("Input integer: ");
    (void)scanf("%d", &a);
    printf("Input integer: ");
    (void)scanf("%d", &b);

    if (a < b) {
        a = a^b;
        b = a^b;
        a = a^b;
    }

    i = b;
    ans = 0;

    do {
        ans += i++;
    } while (i <= a);

    printf("Sum of all integer between %d and %d is %d.\n", b, a, ans);

    return 0;
}