View Compilation Error

0_0_13399459_14193.cpp: In function 'int main()':
0_0_13399459_14193.cpp:26:21: error: 'strlen' was not declared in this scope
   for(i=0;i<strlen(a);i++)
                     ^
0_0_13399459_14193.cpp:49:20: error: 'strlen' was not declared in this scope
   cout<<dp[strlen(a)-1][strlen(b)-1]<<endl;
                    ^