#include <stdio.h>
#include <math.h>
#include <stdlib.h>

typedef struct
{
    long int numerator;
    long int denominator;
    int corrapted;
    int infinity;
} rational_t;

static long int gcd(long int a, long int b)
{
    if (b == 0)
        return labs(a);
    return gcd(b, a % b);
}

void add(long int a_num, long int a_den, long int b_num, long int b_den)
{
    rational_t flag_inf;
    long int nod = gcd(labs(a_den), labs(b_den));
    if (nod == 1)
        printf("%ld\n", (a_num * b_den + b_num * a_den)/(a_den * b_den));
    else
        if (nod == 0)
        {
            flag_inf.infinity = 1;
        }
        else
            printf("%ld\n", (a_num * (b_den/nod) + b_num * (a_den/nod))/((b_den/nod)*a_den));
}

int main()
{
    rational_t first, second;
    first.numerator = 4;
    first.denominator = 7;
    second.numerator = 2;
    second.denominator = 21;
    add(first.numerator, first.denominator, second.numerator, second.denominator);
    return 0;


}