//*********initialization************

v1 = 4.5;                              // change in rocket vel. stage 1.
v2 = 4.5;                              // change in rocket vel. stage 2.
ratio=0.1;                             // ratio of sturcture being 10% of fuel weight
x1 = v1/exhaust_vel;
x2 = v2/exhaust_vel;
r1 = exp(x1);                          // the mass ratio of first stage
r2 = exp(x2);
c = (1+ratio-ratio*r2)/r2;            // expressions used in payload expression for fuel
d = (1+ratio-ratio*r1)/r1;
e = (1-1/r1);
f = (1-1/r2);

a = c*d;                              // expressions used with payload for fuel
b = e+f*d;

double The_fuel_wt = (b/a)*payload_wt;   // declare and initialize fuel

return The_fuel_wt;                      // return found fuel weight
}

//**************Start MAIN***************
int main()
{