View Compilation Error

0_0_35316578_31226.c: In function 'fun':
0_0_35316578_31226.c:7:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for(int i = 3; i <= 20; i++)
     ^
0_0_35316578_31226.c:7:5: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code
0_0_35316578_31226.c: In function 'sum':
0_0_35316578_31226.c:13:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for(int i = 0; i <= 20; i++)
     ^
0_0_35316578_31226.c:15:13: error: redefinition of 'i'
     for(int i = 2; i <= 20; i++)
             ^
0_0_35316578_31226.c:13:13: note: previous definition of 'i' was here
     for(int i = 0; i <= 20; i++)
             ^
0_0_35316578_31226.c:15:5: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
     for(int i = 2; i <= 20; i++)
     ^
0_0_35316578_31226.c:16:9: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
         for(int j = 1; j < i; j++)
         ^