Do-While

#include <stdio.h>
//Slide 13.
int main(){
    int a, b, soma = 0, cont;
    scanf("%d %d", &a, &b);
    do{
        cont = a + 1;
        soma = cont + soma;
        a = a + 1;
    }while(a < (b-1));
    printf("%d", soma);
    return 0;
}