View Compilation Error

0_0_23700596_21665.cpp: In function 'double solve(int, int)':
0_0_23700596_21665.cpp:43:13: error: expected ',' or ';' before 'for'
             for(int i = l; i < r; i++){
             ^
0_0_23700596_21665.cpp:43:28: error: 'i' was not declared in this scope
             for(int i = l; i < r; i++){
                            ^