For example, I enter "N2 + H2" and it gives me "N2 + H2 → NH3".
Or "C10H8 + O2" and it shows "C10H8 + O2 → CO2 + H2O".
I don't need coefficient calculator, where I type full reaction and it calculates coefficients (marked bold in next example):
C10H8 + 12 O2 = 10 CO2 + 4 H2O.