#include <bits/stdc++.h>   using namespace std;   int INF = 1234567890;   int t, T;   int fa[100000], opp[100000];   int l[100000], r[100000];   int col[100000];   set<pair<int, int> > rp;   set<pair<int, int> > lp;   int find(int a) {     if (a == -1) return -1;     if (fa[a] == -1) return a;     return fa[a] = find(fa[a]);   }   bool check(int a, int b) {     if (a == -1 || b == -1) return true;     if (a == b) return false;     return r[a] + r[b] >= t && l[a] + l[b] <= T;   }   bool merge(int a, int b) {     if (a == b) return true;     if (a == -1 || b == -1) return true;     fa[b] = a;     lp.erase(make_pair(l[b], b));     rp.erase(make_pair(r[b], b));     if (l[b] > l[a]) {       if (lp.find(make_pair(l[a], a)) != lp.end()) {         lp.erase(make_pair(l[a], a));         lp.insert(make_pair(l[b], a));       }       l[a] = l[b];     }     if (r[b] < r[a]) {       if (rp.find(make_pair(r[a], a)) != rp.end()) {         rp.erase(make_pair(r[a], a));         rp.insert(make_pair(r[b], a));       }       r[a] = r[b];     }     return l[a] <= r[a];   }   bool diff(int a, int b) {     a = find(a);     b = find(b);     int aa = find(opp[a]);     int bb = find(opp[b]);     if (a == b) return false;     if (!check(a, b)) return false;     if (!check(aa, bb)) return false;     if (opp[a] == -1) opp[a] = b;     if (opp[b] == -1) opp[b] = a;     return merge(aa, b) && merge(a, bb);   }   bool same(int a, int b) {     a = find(a);     b = find(b);     int aa = find(opp[a]);     int bb = find(opp[b]);     if (!check(a, bb)) return false;     if (!check(aa, b)) return false;     if (opp[a] == -1) opp[a] = opp[b];     if (opp[b] == -1) opp[b] = opp[a];     return merge(a, b) && merge(aa, bb);   }   int get(int a) {     if (col[a] != -1) return col[a];     if (fa[a] == -1) {       col[a] = 0;       if (opp[a] != -1) col[find(opp[a])] = 1;       return 0;     }     return col[a] = get(find(a));   }   int main() {     while (scanf( %d%d , &t, &T) == 2) {       rp.clear();       lp.clear();       int n, m;       scanf( %d%d , &n, &m);       bool f = true;       memset(fa, -1, sizeof(fa));       memset(opp, -1, sizeof(opp));       for (int i = 0; i < n; i++) {         scanf( %d%d , l + i, r + i);         rp.insert(make_pair(r[i], i));         lp.insert(make_pair(l[i], i));         if (l[i] > T) f = false;       }       while (m--) {         int a, b;         scanf( %d%d , &a, &b);         a--;         b--;         a = find(a);         b = find(b);         if (!diff(a, b)) f = false;       }       if (n == 1) {         if (l[0] > T || r[0] < t)           printf( IMPOSSIBLE n );         else           printf( POSSIBLE n%d 0 n1 n , max(l[0], t));         continue;       }       for (int i = 0; i < n && f; i++) {         if (find(i) != i) continue;         rp.erase(rp.find(make_pair(r[i], i)));         lp.erase(lp.find(make_pair(l[i], i)));         while (f && !lp.empty()) {           set<pair<int, int> >::iterator itr = lp.end();           itr--;           int b = find(itr->second);           if (b == find(opp[i])) {             b = itr->second;             rp.erase(make_pair(r[b], b));             lp.erase(make_pair(l[b], b));             continue;           }           if (r[i] < l[b])             f = diff(i, b);           else             break;         }         while (f && !lp.empty()) {           set<pair<int, int> >::iterator itr = lp.end();           itr--;           int b = find(itr->second);           if (b == find(opp[i])) {             b = itr->second;             rp.erase(make_pair(r[b], b));             lp.erase(make_pair(l[b], b));             continue;           }           if (l[i] + l[b] > T)             f = same(i, b);           else             break;         }         while (f && !lp.empty()) {           set<pair<int, int> >::iterator itr = rp.begin();           int b = find(itr->second);           if (b == find(opp[i])) {             b = itr->second;             rp.erase(make_pair(r[b], b));             lp.erase(make_pair(l[b], b));             continue;           }           if (r[i] + r[b] < t)             f = same(i, b);           else             break;         }         if (i == find(i)) {           rp.insert(make_pair(r[i], i));           lp.insert(make_pair(l[i], i));         }         if (opp[i] != -1) {           int j = find(opp[i]);           rp.insert(make_pair(r[j], j));           lp.insert(make_pair(l[j], j));         }       }       if (!f)         printf( IMPOSSIBLE n );       else {         printf( POSSIBLE n );         memset(col, -1, sizeof(col));         int l0 = 0, r0 = T, l1 = 0, r1 = T;         for (int i = 0; i < n; i++) {           if (get(i)) {             l1 = max(l1, l[i]);             r1 = min(r1, r[i]);           } else {             l0 = max(l0, l[i]);             r0 = min(r0, r[i]);           }         }         int L = l0, R = l1;         int ndd = t - l0 - l1;         if (ndd > 0) {           if (ndd + L <= r0) {             L += ndd;           } else {             L = r0;             ndd -= r0 - l0;             R += ndd;           }         }         printf( %d %d n , L, R);         for (int i = 0; i < n; i++) printf( %d , col[i] + 1);         printf(  n );       }     }   }