View Compilation Error

0_0_15342318_21048.cpp: In function 'int main()':
0_0_15342318_21048.cpp:52:11: error: redeclaration of 'double t1'
    double t1=len/v1;
           ^
0_0_15342318_21048.cpp:51:11: note: 'double t1' previously declared here
    double t1=len/v1;
           ^