1 #include <stdio.h>
2 #include <stdlib.h>
3 
4 int total = 0;
5 
6 int inc(int x) {
7   switch (x) {
8     case 0: total += 1 + 0; return 1;
9     case 1: total += 1 + 1; return 2;
10     case 2: total += 1 + 2; return 3;
11     case 3: total += 1 + 3; return 4;
12     case 4: total += 1 + 4; return 5;
13     case 5: total += 1 + 5; return 6;
14     default: return x + 1;
15   }
16 }
17 
18 int inc_dup(int x) {
19   switch (x) {
20     case 0: total += 2 + 0; return 1;
21     case 1: total += 2 + 1; return 2;
22     case 2: total += 2 + 2; return 3;
23     case 3: total += 2 + 3; return 4;
24     case 4: total += 2 + 4; return 5;
25     case 5: total += 2 + 5; return 6;
26     default: return x + 1;
27   }
28 }
29 
30 int main() {
31   int c = 0;
32   for (int i = 0; i < 10000000; ++i) {
33     int a = rand() % 7;
34     int b = rand() % 7;
35     c += inc(a) - 2*inc_dup(b);
36   }
37   return c == 0;
38 }
39