{"raw_statement":[{"iden":"problem statement","content":"Hearing that energy drinks increase rating in those sites, Takahashi decides to buy up $M$ cans of energy drinks.\nThere are $N$ stores that sell energy drinks. In the $i$\\-th store, he can buy at most $B_i$ cans of energy drinks for $A_i$ yen (the currency of Japan) each.\nWhat is the minimum amount of money with which he can buy $M$ cans of energy drinks?\nIt is guaranteed that, in the given inputs, a sufficient amount of money can always buy $M$ cans of energy drinks."},{"iden":"constraints","content":"*   All values in input are integers.\n*   $1 \\leq N, M \\leq 10^5$\n*   $1 \\leq A_i \\leq 10^9$\n*   $1 \\leq B_i \\leq 10^5$\n*   $B_1 + ... + B_N \\geq M$"},{"iden":"input","content":"Input is given from Standard Input in the following format:\n\n$N$ $M$\n$A_1$ $B_1$\n$A_2$ $B_2$\n$\\vdots$\n$A_N$ $B_N$"},{"iden":"sample input 1","content":"2 5\n4 9\n2 4"},{"iden":"sample output 1","content":"12\n\nWith $12$ yen, we can buy one drink at the first store and four drinks at the second store, for the total of five drinks. However, we cannot buy $5$ drinks with $11$ yen or less."},{"iden":"sample input 2","content":"4 30\n6 18\n2 5\n3 10\n7 9"},{"iden":"sample output 2","content":"130"},{"iden":"sample input 3","content":"1 100000\n1000000000 100000"},{"iden":"sample output 3","content":"100000000000000\n\nThe output may not fit into a $32$\\-bit integer type."}],"translated_statement":null,"sample_group":[],"show_order":["default"],"formal_statement":null,"simple_statement":null,"has_page_source":true}