Main.cc: In function 'int main()':
Main.cc:5:10: error: 'm' was not declared in this scope
cin>>m>>n;
^
Main.cc:6:23: error: expected ';' before ')' token
for(int i=m;n<=i++){
^
Main.cc:4:9: warning: unused variable 'mn' [-Wunused-variable]
int mn,n,sum;
^