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BLOPER.cpp
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BLOPER.cpp
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/*My First Template :D*/
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> ii;
#define MOD (ll)1000000007
#define pb push_back
#define EPS 1e-9
#define FOR(i,n) for(int i = 0;i < n; i++)
#define FORE(i,a,b) for(int i = a;i <= b; i++)
#define tr(container, it) for(typeof(container.begin()) it = container.begin(); it != container.end(); it++)
#define io ios_base::sync_with_stdio(false);cin.tie(NULL);
#define endl '\n'
#define F first
#define S second
#define sp ' '
# define M_PI 3.14159265358979323846
template <typename T> T gcd(T a, T b){return (b==0)?a:gcd(b,a%b);}
template <typename T> T lcm(T a, T b){return a*(b/gcd(a,b));}
template <typename T> T mod_exp(T b, T p, T m){T x = 1;while(p){if(p&1)x=(x*b)%m;b=(b*b)%m;p=p>>1;}return x;}
template <typename T> T invFermat(T a, T p){return mod_exp(a, p-2, p);}
template <typename T> T exp(T b, T p){T x = 1;while(p){if(p&1)x=(x*b);b=(b*b);p=p>>1;}return x;}
const int MAXN = 1e5+5;
int main(){
io;
int n, s;
cin >> n >> s;
int maxS = (n*(n+1))/2;
int minS = 2-(n*(n+1))/2;
if(s < 0){
if(s < minS)
cout << "Impossible" << endl;
else{
int rem = maxS+s;
if(rem&1)
cout << "Impossible" << endl;
else{
// search for positives
int currSum = rem/2 - 1;
int sign[n+1];
FORE(i,1,n) sign[i] = 0;
sign[1] = 1;
int idx = n;
// building positive sum
while(idx > 1 && currSum){
if(currSum-idx == 0){
currSum = 0;
sign[idx] = 1;
break;
}
if(currSum-idx > 1){
currSum -= idx;
sign[idx] = 1;
}else{
sign[idx] = 0;
}
idx--;
}
if(currSum)
cout << "Impossible" << endl;
else{
cout << "1";
FORE(i,2,n){
if(sign[i]){
cout << "+";
}else{
cout << "-";
}
cout << i;
}
}
}
}
}else{
if(s > maxS){
cout << "Impossible" << endl;
}else{
int rem = maxS-s;
if(rem&1){
cout << "Impossible" << endl;
}else{
// divide in equal parts
int currSum = rem/2;
int sign[n+1];
FORE(i,1,n) sign[i] = 1;
sign[1] = 1;
int idx = n;
// building negative sum
while(idx > 1 && currSum){
if(currSum-idx == 0){
currSum = 0;
sign[idx] = 0;
break;
}
if(currSum-idx > 1){
currSum -= idx;
sign[idx] = 0;
}else{
sign[idx] = 1;
}
idx--;
}
if(currSum)
cout << "Impossible" << endl;
else{
cout << "1";
FORE(i,2,n){
if(sign[i]){
cout << "+";
}else{
cout << "-";
}
cout << i;
}
}
}
}
}
return 0;
}