#include <bits/stdc++.h>   using namespace std;   long long int a, b;   long long int x, y;   long long int n, t;   bool flag = false;   string str;   int main() {     long long int a[4];     cin >> a[0] >> a[1] >> a[2] >> a[3];     sort(a, a + 4);     if ((a[0] + a[1] < a[2]) && (a[1] + a[2] < a[3]))       str =  IMPOSSIBLE ;     else if (a[0] + a[1] > a[2] || a[1] + a[2] > a[3])       str =  TRIANGLE ;     else       str =  SEGMENT ;     cout << str;     return 0;   }   