#include <bits/stdc++.h>   using namespace std;   int a[4];   int main() {     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]) {       cout <<  TRIANGLE ;       return 0;     } else if (a[0] + a[1] == a[2] || a[1] + a[2] == a[3]) {       cout <<  SEGMENT ;       return 0;     } else       cout <<  IMPOSSIBLE ;     return 0;   }   