Using int 128 in C++

#include<bits/stdc++.h>
using namespace std;

#ifdef forthright48
    #define myint long long
#else
    #define myint __int128
#endif

/// Print a __int128 value:
void print_myint(myint k){
    if(k == 0){
        printf("0");
    }else{
        if(k < 0){
            k = -k;
            printf("-");
        }
        vector<int> v;
        myint ten = 10;
        while(k > 0){
            v.push_back(k%ten);
            k /= ten;
        }
        reverse(v.begin(), v.end());
        for(int i = 0; i<v.size(); i++){
            printf("%d",v[i]);
        }
    }
}

/// Take input a __int128 value:
myint input_myint(){
    char s[130];
    scanf("%s",s);
    myint k = 0, ten = 10;
    int i = 0;
    while(s[i]){
        myint d = (s[i] - '0');
        k = k * ten + d;
        i++;
    }
    return k;
}

int main(){
    myint k = input_myint();
    print_myint(k);
    printf("\n");
    return 0;
}