/in/foo.cc: In function 'int sum(int*, int)':
/in/foo.cc:16:20: warning: left operand of comma operator has no effect [-Wunused-value]
for(int i = 1 ; i <= n, i++ ){
~~^~~~
/in/foo.cc:16:30: error: expected ';' before ')' token
for(int i = 1 ; i <= n, i++ ){
^
/in/foo.cc: In function 'int main()':
/in/foo.cc:25:8: error: unable to find numeric literal operator 'operator""n'
int a[2n+1];
^~
/in/foo.cc:25:8: note: use -std=gnu++11 or -fext-numeric-literals to enable more built-in suffixes
/in/foo.cc:27:16: error: 'a' was not declared in this scope
scanf("%d", &a[i]);
^
/in/foo.cc:35:46: error: 'a' was not declared in this scope
if(f[i][j]< (f[i][k] + f[k + 1][j] + sum(a,j) - sum(a,i-1))){
^