Matching rownumber and column name of a data frame with values of another data frame

I have a sample data frame

samp_df <- data.frame(x1=c(1,3,5,7,9),x2=c(2,4,6,8,10))> samp_df  x1 x21  1  22  3  43  5  64  7  85  9 10

I have another data frame which contains variable str and sis_str

samp2_df <- data.frame(str=c(x1,x1,x2,x2,x1),sis_str=c(1,2,4,5,3))> samp2_df  str sis_str1   x1       12   x1       23   x2       44   x2       55   x1       3

The objective is to create another variable "sim" in the samp2_df data frame which contains the value from samp_df,such that the variable sis_str should match the row name of the first data frame and variable str should match the column name of the first data frame

So the output should be

> samp2_df  str sis_str  sim1   1       1   12   1       2   33   2       4   84   2       5   105   1       3   5