struct BigInteger {
    int sign;
    char number[100];
};

void swap (struct BigInteger * a, struct BigInteger * b) {
    struct BigInteger temp;
    temp = *a;
    *a = *b;
    *b = temp;
}

void swapstr(char * a, char * b) {
    char temp = *a;
    *a = *b;
    *b = temp;
}

void reverse(char* str) {
    int i;
    for(i=0;i<strlen(str)/2;i++) swapstr(str+i,str+strlen(str)-1-i);
}

struct BigInteger sum(struct BigInteger first, struct BigInteger second) {
    int i,j;
    if(strlen(first.number) < strlen(second.number)) swap(&first, &second);
    char newSum[100];
    reverse(first.number); reverse(second.number);
    if (first.sign == second.sign) {
        int nho = 0;
        for(i=0;i<strlen(second.number);i++) {
            int sum = first.number[i]-'0' + second.number[i]-'0';
            if (nho == 1) {
                sum++;
                nho = 0;
            }
            if (sum >= 10) {
                nho = 1;
                sum-=10;
            }
            newSum[i] = sum+'0';
        }
        if (strlen(first.number) == strlen(second.number))
            if (nho == 1) newSum[i] = '1';
        else {
            for(;i<strlen(first.number);i++) {
                newSum[i]=first.number[i];
                if (nho == 1) {
                    newSum[i]++;
                    nho = 0;;
                }
            }
        }
        reverse(newSum);
        struct BigInteger tong;
        if (first.sign == 0) tong.sign = 0;
        else tong.sign = 1;
        strcpy(tong.number, newSum);
        return tong;
    } else {
        if (strlen(first.number) == strlen(second.number)) {
            for(i=strlen(first.number)-1;i>=0;i--) {
                if (first.number[i] < second.number[i]) {
                    swap(&first, &second);
                    break;
                } else if(first.number[i] > second.number[i]) break;
            }
        }
        int nho = 0;
        for(i=0;i<strlen(second.number);i++) {
            int sum = first.number[i]-'0' - (second.number[i]-'0');
            if (nho == 1) {
                sum--;
                nho = 0;
            }
            if (sum < 0) {
                nho = 1;
                sum+=10;
            }
            newSum[i] = sum+'0';
        }
        if (strlen(first.number) > strlen(second.number))
            for(;i<strlen(first.number);i++) {
                newSum[i]=first.number[i];
                if (nho == 1) {
                    newSum[i]--;
                    nho = 0;
                }
            }
        reverse(newSum);
        struct BigInteger tong;
        if (first.sign == 1) tong.sign = 1;
        else tong.sign = 0;
        strcpy(tong.number, newSum);
        return tong;
    }
}