View Compilation Error

0_0_38962612_12903.cpp: In function 'int main()':
0_0_38962612_12903.cpp:5:3: error: 'PI' was not declared in this scope
    5 | t=PI*a*a;
      |   ^~
0_0_38962612_12903.cpp:6:16: error: expected '}' at end of input
    6 | printf("%f",t);
      |                ^
0_0_38962612_12903.cpp:3:1: note: to match this '{'
    3 | {float a,t;
      | ^