View Compilation Error

0_0_20893300_15573.c: In function 'sum':
0_0_20893300_15573.c:5:2: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
  for(int i=1;i<=a;i++){
  ^
0_0_20893300_15573.c:5:2: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code