#include 
#include 
int main(int argc, const char * argv[]) {
    int a, b;
    scanf("%d%d", &a, &b);

    int i = a;
    int zbir = 0;

    while(i <= b) {
        if(i % 2 == 1) {
            zbir += i;
        }
        i++;
    }
    printf("%d ", zbir);

    
    return 0;