/* flight scheduling LP relaxation: fractional solution */ min: x1+ x2+ x3+ x4+ 3 x5+ 3 x6+ 3 x7+ 2 x8+ 2 x9+ +x10+x11+ x12 + x13 + 2 x14 + 2 x15 +x16+ x17 + x18 +x19+ x20 + x21 +x22; c1:x1+x2+x3+x4+x5+x6+x7+x8+x9 +x21 >= 1; c2:x1+x2+x3+x8+x9+x10+x11+x16+x17 >= 1; c3:x2+x4+x6+x7+x8+x9+x10+x12+x14+x15+x16+x17 +x19 +x20 >= 1; c4:x3+x5+x11+x13 >= 1; c5:x6+x8+x14+x16 +x19>= 1; c6:x7+x9+x15+x17+x18+x20 >= 1; c7:x4+x5+x6+x7+x12+x13+x14+x15+x21 >= 1; c8:x18+x22 >=1;