View Compilation Error

0_0_25007004_31147.cpp: In function 'int solve(int, int, int)':
0_0_25007004_31147.cpp:23:13: error: 'sum' was not declared in this scope
             sum++;
             ^
0_0_25007004_31147.cpp:25:13: error: 'sum' was not declared in this scope
         if (sum) {
             ^