#include <iostream>
using namespace std;
inline int bit(int a, int n) {if(n > 31) return 0; return (a & ( 1 << n )) >> n; }
int main(){
int A = 19;
int B = 7;
int X = 0;
int carryover = 0;
int aCurrent, aNext, bCurrent, bNext;
for(int i = 0; i < 32; i++){
aCurrent = bit(A, i); bCurrent = bit(B, i);
aNext = bit(A, i + 1); bNext = bit(B, i + 1);
cout<<"A["<<i<<"] = "<<aCurrent<<", "<<"B["<<i<<"] = "<<bCurrent<<", carryover = "<<carryover<<endl;
if(aCurrent == 0 && bCurrent == 0){
if(carryover) {X = -1; break;}
if(aNext != bNext){
cout<<"\tX["<<i<<"] must be 1"<<endl;
X += 1 << i;
}
else cout<<"\tX["<<i<<"] will be 0"<<endl;
carryover = 0;
}
else if(aCurrent == 0 && bCurrent == 1){
if(!carryover) {X = -1; break;}
if(aNext == bNext){
cout<<"\tX["<<i<<"] must be 1"<<endl;
X += 1 << i;
}
else cout<<"\tX["<<i<<"] will be 0"<<endl;
carryover = 1;
}
else if(aCurrent == 1 && bCurrent == 0){
if(!carryover) {X = -1; break;}
if(aNext != bNext){
cout<<"\tX["<<i<<"] must be 1"<<endl;
X += 1 << i;
carryover = 1;
}
else {
cout<<"\tX["<<i<<"] will be 0"<<endl;
carryover = 0;
}
}
else if(aCurrent == 1 && bCurrent == 1){
if(carryover) {X = -1; break;}
if(aNext != bNext){
cout<<"\tX["<<i<<"] must be 1"<<endl;
X += 1 << i;
carryover = 1;
}
else {
cout<<"\tX["<<i<<"] will be 0"<<endl;
carryover = 0;
}
}
}
if(X != -1) cout<<"X = "<<X<<endl;
else cout<<"X doesnt exist"<<endl;
return 0;
}
