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// 1) count increasing triples
	for(int j = 0; j < n; j++) {
		int smaller = 0, bigger = 0;
		for(int i = 0; i < j; i++) {
			if(a[i] < a[j]) {
				smaller++;
			}
		}
		for(int k = j + 1; k < n; k++) {
			if(a[k] > a[j]) {
				bigger++;
			}
		}
		answer += smaller * bigger;
	}
 
 
// 4-SUM
set<int> pairs; // pairs up to i-1
for(int i = 0; i < n; i++) {
	for(int j = i + 1; j < n; j++) {
		int missing = x - a[i] - a[j];
		if(pairs.count(missing)) {
			printf("YES");
			return 0;
		}
	}
	for(int z = 0; z < i; z++) {
		pairs.insert(a[z] + a[i]);
	}
}

prog.cpp:2:2: error: expected unqualified-id before ‘for’
  for(int j = 0; j < n; j++) {
  ^~~
prog.cpp:2:17: error: ‘j’ does not name a type
  for(int j = 0; j < n; j++) {
                 ^
prog.cpp:2:24: error: ‘j’ does not name a type
  for(int j = 0; j < n; j++) {
                        ^
prog.cpp:19:1: error: ‘set’ does not name a type
 set<int> pairs; // pairs up to i-1
 ^~~
prog.cpp:20:1: error: expected unqualified-id before ‘for’
 for(int i = 0; i < n; i++) {
 ^~~
prog.cpp:20:16: error: ‘i’ does not name a type
 for(int i = 0; i < n; i++) {
                ^
prog.cpp:20:23: error: ‘i’ does not name a type
 for(int i = 0; i < n; i++) {
                       ^

Standard output is empty