what = input( "Cto delaem? (+, -): " )
a = float( input( "1 chislo: " ) )
b = float( input( "2 chislo: " ) )
d = float( input( "2 chislo: " ) )
if what == "+":
c = a + b + d
print("rez: " + str(c))
elif what == "-":
c = a - b
print("rez: " + str(c))
else:
print("error")
input()