def mass(element):
   mass = {
   'H':'1.00797',
   'He':'4.0026',
   'Li':'6.941',
   'Be':'9.01218',
   'B':'10.81',
   'C':'12.011',
   'N':'14.0067',
   'O':'15.9994',
   'F':'18.998403',
   'Ne':'20.179',
   'Na':'22.98977',
   'Mg':'24.305',
   'Al':'26.98154',
   'Si':'28.0855',
   'P':'30.97376',
   'S':'32.06',
   'Cl':'35.453',
   'K':'39.0983',
   'Ar':'39.948',
   'Ca':'40.08',
   'Sc':'44.9559',
   'Ti':'47.9',
   'V':'50.9415',
   'Cr':'51.996',
   'Mn':'54.938',
   'Fe':'55.847',
   'Ni':'58.7',
   'Co':'58.9332',
   'Cu':'63.546',
   'Zn':'65.38',
   'Ga':'69.72',
   'Ge':'72.59',
   'As':'74.9216',
   'Se':'78.96',
   'Br':'79.904',
   'Kr':'83.8',
   'Rb':'85.4678',
   'Sr':'87.62',
   'Y':'88.9059',
   'Zr':'91.22',
   'Nb':'92.9064',
   'Mo':'95.94',
   'Ru':'101.07',
   'Rh':'102.9055',
   'Pd':'106.4',
   'Ag':'107.868',
   'Cd':'112.41',
   'In':'114.82',
   'Sn':'118.69',
   'Sb':'121.75',
   'I':'126.9045',
   'Te':'127.6',
   'Xe':'131.3',
   'Cs':'132.9054',
   'Ba':'137.33',
   'La':'138.9055',
   'Ce':'140.12',
   'Pr':'140.9077',
   'Nd':'144.24',
   'Sm':'150.4',
   'Eu':'151.96',
   'Gd':'157.25',
   'Tb':'158.9254',
   'Dy':'162.5',
   'Ho':'164.9304',
   'Er':'167.26',
   'Tm':'168.9342',
   'Yb':'173.04',
   'Lu':'174.967',
   'Hf':'178.49',
   'Ta':'180.9479',
   'W':'183.85',
   'Re':'186.207',
   'Os':'190.2',
   'Ir':'192.22',
   'Pt':'195.09',
   'Au':'196.9665',
   'Hg':'200.59',
   'Tl':'204.37',
   'Pb':'207.2',
   'Bi':'208.9804',
   'Ra':'226.0254',
   'Ac':'227.0278',
   'Pa':'231.0359',
   'Th':'232.0381',
   'Np':'237.0482',
   'U':'238.029'
}

   return mass[element]