Main.cc: In function 'int main()':
Main.cc:6:19: error: 'm' was not declared in this scope
for(int i = a;i<=m;i++){
^
Main.cc:4:8: warning: unused variable 'b' [-Wunused-variable]
int a,b,sum=0;
^
Main.cc:4:10: warning: unused variable 'sum' [-Wunused-variable]
int a,b,sum=0;
^