Problem.G

#include <stdio.h>
#include <stdlib.h>
typedef long long LL;
LL gcd(LL x, LL y){
    return x % y ? gcd(y, x % y) : y;
}
int main(){
    LL a1, b1, a2, b2, a, b, g, s;
    int op;
    char input[256] = { 0 };
    while(fgets(input, 255, stdin)){
        sscanf(input, "%lld/%lld %lld/%lld %d", &a1, &b1, &a2, &b2, &op);
        switch(op){
        case 1:
            a = (a1 * b2 + b1 * a2);
            b = b1 * b2;
            break;
        case 2:
            a = (a1 * b2 - b1 * a2);
            b = b1 * b2;
            break;
        case 3:
            a = a1 * a2;
            b = b1 * b2;
            break;
        case 4:
            a = a1 * b2;
            b = b1 * a2;
            break;
        default:
            break;
        }
        if(a < 0 || b < 0){
            s = 1;
        }
        else{
            s = 0;
        }
        a = llabs(a);
        b = llabs(b);
        g = gcd(a, b);
        if(g == b){
            printf("%lld\n", a / b);
        }
        else{
            if(s){
                putchar('-');
            }
            if(g != 1){
                printf("%lld/%lld\n", a / g, b / g);
            }
            else{
                printf("%lld/%lld\n", a, b);
            }
        }
    }
    return 0;
}