Help with this stupid error -.-

I'm just getting into programming and was wondering if someone out there in the community could help.

To start, I'm making a Rock-Paper-Scissors game with a sort of "scoreboard" in it.
When I try to compile it, however, this stupid error pops up:

"error C2106: '=' : left operand must be l-value

Here's that little snippet of the code and what I have used as header files (and other things):

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int main()
{
int a, b, c, d, e, f;

d = 0;
e = 0;
f = 0;

...

if ( a == b ) {
cout<<"It's a tie!\nBoth of you picked the same thing!\n";
f + 1 = f;
}

if (( a == 1 && b == 3 ) || ( a == 2 && b == 1 ) || ( a == 3 && b == 2 )){
cout<<"You won!\n";
d + 1 = d;
}
else if ( a != b ) {
cout<<"The computer won!\n";
e + 1 = e;
}
...

Would someone care to help!

EDIT (MAJOR):
AHHHH! Stupid, stupid, stupid!

e = e + 1
etc.

God... I hate myself.