View Compilation Error

0_0_25093648_4882.c: In function 'sum':
0_0_25093648_4882.c:18:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for(int l=0; l<6; l++) {
     ^
0_0_25093648_4882.c:18:5: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code