//Variable declaration
e=1.6*10**-19;   //charge of electron(c)
epsilon0=8.85*10**-12;    //permittivity(C/Nm)
r0=2.5*10**-10;     //seperation(m)

//Calculation
PE=e**2/(4*e*%pi*epsilon0*r0);     //potential energy(eV)

//Result
printf('potential energy is %0.3f   eV  \n',(PE))